feat(i18n): add RegisterLocales for package locale registration

- Add i18n.RegisterLocales(fsys, dir) for packages to register translations
- Locales are automatically loaded when i18n.Init() is called
- Fix gram.word.* loading bug (strings were in wrong switch case)
- Fix loadJSON to merge messages instead of replacing
- Add common.* keys to base locale (labels, flags, progress, etc.)
- Add pkg/php/locales with PHP-specific translations
- pkg/php/i18n.go registers locales via init()

This enables the idiomatic pattern where packages register their
locale files and they're automatically loaded by the i18n system.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkg/i18n/hooks.go

@@ -2,12 +2,61 @@
 package i18n
 
 import (
+	"io/fs"
 	"runtime"
+	"sync"
 	"sync/atomic"
 )
 
 var missingKeyHandler atomic.Value // stores MissingKeyHandler
 
+// localeRegistration holds a filesystem and directory for locale loading.
+type localeRegistration struct {
+	fsys fs.FS
+	dir  string
+}
+
+var (
+	registeredLocales   []localeRegistration
+	registeredLocalesMu sync.Mutex
+	localesLoaded       bool
+)
+
+// RegisterLocales registers a filesystem containing locale files to be loaded.
+// Call this in your package's init() to register translations.
+// Locales are loaded when the i18n service initialises.
+//
+//	//go:embed locales/*.json
+//	var localeFS embed.FS
+//
+//	func init() {
+//	    i18n.RegisterLocales(localeFS, "locales")
+//	}
+func RegisterLocales(fsys fs.FS, dir string) {
+	registeredLocalesMu.Lock()
+	defer registeredLocalesMu.Unlock()
+	registeredLocales = append(registeredLocales, localeRegistration{fsys: fsys, dir: dir})
+
+	// If locales already loaded (service already running), load immediately
+	if localesLoaded {
+		if svc := Default(); svc != nil {
+			_ = svc.LoadFS(fsys, dir)
+		}
+	}
+}
+
+// loadRegisteredLocales loads all registered locale filesystems into the service.
+// Called by the service during initialisation.
+func loadRegisteredLocales(svc *Service) {
+	registeredLocalesMu.Lock()
+	defer registeredLocalesMu.Unlock()
+
+	for _, reg := range registeredLocales {
+		_ = svc.LoadFS(reg.fsys, reg.dir)
+	}
+	localesLoaded = true
+}
+
 // OnMissingKey registers a handler for missing translation keys.
 // Called when T() can't find a key in ModeCollect.
 // Thread-safe: can be called concurrently with translations.

pkg/i18n/loader.go

@@ -120,6 +120,12 @@ func flattenWithGrammar(prefix string, data map[string]any, out map[string]Messa
 
 		switch v := value.(type) {
 		case string:
+			// Check if this is a word in gram.word.*
+			if grammar != nil && strings.HasPrefix(fullKey, "gram.word.") {
+				wordKey := strings.TrimPrefix(fullKey, "gram.word.")
+				grammar.Words[strings.ToLower(wordKey)] = v
+				continue
+			}
 			out[fullKey] = Message{Text: v}
 
 		case map[string]any:
@@ -188,19 +194,6 @@ func flattenWithGrammar(prefix string, data map[string]any, out map[string]Messa
 				continue
 			}
 
-			// Check if this is a base word in gram.word.*
-			if grammar != nil && strings.HasPrefix(fullKey, "gram.word.") {
-				wordKey := strings.TrimPrefix(fullKey, "gram.word.")
-				// v could be a string or a nested object
-				if str, ok := value.(string); ok {
-					if grammar.Words == nil {
-						grammar.Words = make(map[string]string)
-					}
-					grammar.Words[strings.ToLower(wordKey)] = str
-				}
-				continue
-			}
-
 			// Check if this is a plural object (has CLDR plural category keys)
 			if isPluralObject(v) {
 				msg := Message{}

pkg/i18n/locales/en_GB.json

@@ -252,6 +252,39 @@
 			"templates.short": "Manage LinuxKit templates"
 		}
 	},
+	"common": {
+		"label": {
+			"done": "Done",
+			"error": "Error",
+			"warning": "Warning",
+			"info": "Info",
+			"fix": "Fix:",
+			"install": "Install:",
+			"summary": "Summary:",
+			"setup": "Setup:"
+		},
+		"flag": {
+			"fix": "Auto-fix issues where possible",
+			"diff": "Show diff of changes",
+			"json": "Output as JSON"
+		},
+		"progress": {
+			"running": "Running {{.Task}}...",
+			"checking": "Checking {{.Item}}..."
+		},
+		"result": {
+			"no_issues": "No issues found"
+		},
+		"success": {
+			"completed": "{{.Action}} successfully"
+		},
+		"error": {
+			"failed": "Failed to {{.Action}}"
+		},
+		"hint": {
+			"fix_deps": "Update dependencies to fix vulnerabilities"
+		}
+	},
 	"error": {
 		"gh_not_found": "'gh' CLI not found. Install from https://cli.github.com/",
 		"registry_not_found": "No repos.yaml found",

pkg/i18n/service.go

@@ -152,6 +152,8 @@ func Init() error {
 		svc, err := New()
 		if err == nil {
 			defaultService.Store(svc)
+			// Load any locales registered by packages before Init was called
+			loadRegisteredLocales(svc)
 		}
 		defaultErr = err
 	})
@@ -177,6 +179,7 @@ func SetDefault(s *Service) {
 
 // loadJSON parses nested JSON and flattens to dot-notation keys.
 // Also extracts grammar data (verbs, nouns, articles) for the language.
+// If messages already exist for the language, new messages are merged in.
 func (s *Service) loadJSON(lang string, data []byte) error {
 	var raw map[string]any
 	if err := json.Unmarshal(data, &raw); err != nil {
@@ -191,7 +194,15 @@ func (s *Service) loadJSON(lang string, data []byte) error {
 	}
 
 	flattenWithGrammar("", raw, messages, grammarData)
-	s.messages[lang] = messages
+
+	// Merge new messages into existing (or create new map)
+	if existing, ok := s.messages[lang]; ok {
+		for key, msg := range messages {
+			existing[key] = msg
+		}
+	} else {
+		s.messages[lang] = messages
+	}
 
 	// Store grammar data if any was found
 	if len(grammarData.Verbs) > 0 || len(grammarData.Nouns) > 0 || len(grammarData.Words) > 0 {

pkg/php/i18n.go

@@ -0,0 +1,16 @@
+// Package php provides PHP/Laravel development tools.
+package php
+
+import (
+	"embed"
+
+	"github.com/host-uk/core/pkg/i18n"
+)
+
+//go:embed locales/*.json
+var localeFS embed.FS
+
+func init() {
+	// Register PHP translations with the i18n system
+	i18n.RegisterLocales(localeFS, "locales")
+}

pkg/php/locales/en_GB.json

@@ -0,0 +1,147 @@
+{
+	"cmd": {
+		"php": {
+			"short": "Laravel/PHP development tools",
+			"long": "Laravel and PHP development tools including testing, formatting, static analysis, and deployment",
+			"label": {
+				"php": "PHP:",
+				"audit": "Audit:",
+				"psalm": "Psalm:",
+				"rector": "Rector:",
+				"security": "Security:",
+				"infection": "Infection:",
+				"info": "Info:",
+				"setup": "Setup:"
+			},
+			"error": {
+				"not_php": "Not a PHP project (no composer.json found)",
+				"fmt_failed": "Formatting failed",
+				"fmt_issues": "Style issues found",
+				"analysis_issues": "Analysis errors found",
+				"audit_failed": "Audit failed",
+				"vulns_found": "Vulnerabilities found",
+				"psalm_not_installed": "Psalm not installed",
+				"psalm_issues": "Psalm found type errors",
+				"rector_not_installed": "Rector not installed",
+				"rector_failed": "Rector failed",
+				"infection_not_installed": "Infection not installed",
+				"infection_failed": "Mutation testing failed",
+				"security_failed": "Security check failed",
+				"critical_high_issues": "Critical or high severity issues found"
+			},
+			"test": {
+				"short": "Run PHPUnit/Pest tests",
+				"long": "Run PHPUnit or Pest tests with optional filtering, parallel execution, and coverage",
+				"flag": {
+					"parallel": "Run tests in parallel",
+					"coverage": "Generate code coverage report",
+					"filter": "Filter tests by name",
+					"group": "Run only tests in this group"
+				}
+			},
+			"fmt": {
+				"short": "Format PHP code with Laravel Pint",
+				"long": "Format PHP code using Laravel Pint code style fixer",
+				"no_formatter": "No code formatter found (install laravel/pint)",
+				"no_issues": "No style issues found",
+				"formatting": "Formatting with {{.Formatter}}...",
+				"flag": {
+					"fix": "Fix style issues (default: check only)"
+				}
+			},
+			"analyse": {
+				"short": "Run PHPStan static analysis",
+				"long": "Run PHPStan/Larastan for static code analysis",
+				"no_analyser": "No static analyser found (install phpstan/phpstan or nunomaduro/larastan)",
+				"flag": {
+					"level": "Analysis level (0-9, default: from config)",
+					"memory": "Memory limit (e.g., 2G)"
+				}
+			},
+			"audit": {
+				"short": "Security audit for dependencies",
+				"long": "Audit Composer and NPM dependencies for known vulnerabilities",
+				"scanning": "Scanning dependencies for vulnerabilities...",
+				"secure": "No vulnerabilities",
+				"error": "Audit error",
+				"vulnerabilities": "{{.Count}} vulnerabilities found",
+				"found_vulns": "Found {{.Count}} vulnerabilities",
+				"all_secure": "All dependencies secure",
+				"completed_errors": "Audit completed with errors",
+				"flag": {
+					"fix": "Attempt to fix vulnerabilities"
+				}
+			},
+			"psalm": {
+				"short": "Run Psalm static analysis",
+				"long": "Run Psalm for deep static analysis and type checking",
+				"not_found": "Psalm not found",
+				"install": "composer require --dev vimeo/psalm",
+				"setup": "vendor/bin/psalm --init",
+				"analysing": "Analysing with Psalm...",
+				"analysing_fixing": "Analysing and fixing with Psalm...",
+				"flag": {
+					"level": "Analysis level (1-8)",
+					"baseline": "Generate or update baseline",
+					"show_info": "Show informational issues"
+				}
+			},
+			"rector": {
+				"short": "Automated code refactoring",
+				"long": "Run Rector for automated code upgrades and refactoring",
+				"not_found": "Rector not found",
+				"install": "composer require --dev rector/rector",
+				"setup": "vendor/bin/rector init",
+				"analysing": "Analysing code for refactoring opportunities...",
+				"refactoring": "Refactoring code...",
+				"no_changes": "No refactoring changes needed",
+				"changes_suggested": "Rector suggests changes (run with --fix to apply)",
+				"flag": {
+					"fix": "Apply refactoring changes",
+					"diff": "Show diff of changes",
+					"clear_cache": "Clear Rector cache before running"
+				}
+			},
+			"infection": {
+				"short": "Mutation testing for test quality",
+				"long": "Run Infection mutation testing to measure test suite quality",
+				"not_found": "Infection not found",
+				"install": "composer require --dev infection/infection",
+				"note": "This may take a while depending on test suite size",
+				"complete": "Mutation testing complete",
+				"flag": {
+					"min_msi": "Minimum Mutation Score Indicator (0-100)",
+					"min_covered_msi": "Minimum covered code MSI (0-100)",
+					"threads": "Number of parallel threads",
+					"filter": "Filter mutants by file path",
+					"only_covered": "Only mutate covered code"
+				}
+			},
+			"security": {
+				"short": "Security vulnerability scanning",
+				"long": "Run comprehensive security checks on PHP codebase",
+				"checks_suffix": " CHECKS",
+				"summary": "Security scan complete",
+				"passed": "Passed:",
+				"critical": "Critical:",
+				"high": "High:",
+				"medium": "Medium:",
+				"low": "Low:",
+				"flag": {
+					"severity": "Minimum severity to report (low, medium, high, critical)",
+					"sarif": "Output in SARIF format",
+					"url": "Application URL for runtime checks"
+				}
+			},
+			"qa": {
+				"short": "Run full QA pipeline",
+				"long": "Run comprehensive quality assurance: audit, format, analyse, test, and more",
+				"flag": {
+					"quick": "Run quick checks only (audit, fmt, stan)",
+					"full": "Run all stages including slow checks",
+					"fix": "Auto-fix issues where possible"
+				}
+			}
+		}
+	}
+}