feat(i18n): add core.* namespace magic in T()

T() now auto-composes grammar patterns for core.* keys:
- core.label.{word} → "Status:"
- core.progress.{verb} → "Building..."
- core.count.{noun}, n → "5 files"
- core.done.{verb}, subj → "File deleted"
- core.fail.{verb}, subj → "Failed to delete file"

_() and Raw() do direct key lookup without magic.

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

pkg/i18n/i18n.go

@@ -508,13 +508,17 @@ func L(word string) string {
 	return Label(word)
 }
 
-// _ is the standard gettext-style translation helper.
-// Alias for T() - use whichever you prefer.
+// _ is the raw gettext-style translation helper.
+// Unlike T(), this does NOT handle core.* namespace magic.
+// Use this for direct key lookups without auto-composition.
 //
-//	i18n._("cli.success")
-//	i18n._("cli.greeting", map[string]any{"Name": "World"})
+//	i18n._("cli.success")           // Raw lookup
+//	i18n.T("core.label.status")     // Smart: returns "Status:"
 func _(messageID string, args ...any) string {
-	return T(messageID, args...)
+	if svc := Default(); svc != nil {
+		return svc.Raw(messageID, args...)
+	}
+	return messageID
 }
 
 // --- Service methods ---
@@ -616,36 +620,35 @@ func (s *Service) PluralCategory(n int) PluralCategory {
 	return GetPluralCategory(s.currentLang, n)
 }
 
-// T translates a message by its ID.
-// Optional template data can be passed for interpolation.
+// T translates a message by its ID with smart core.* namespace handling.
 //
-// For plural messages, pass a map with "Count" to select the form:
+// # Core Namespace Magic
 //
-//	svc.T("cli.count.items", map[string]any{"Count": 5})
+// The core.* namespace provides auto-composed grammar shortcuts:
 //
-// For semantic intents (core.* namespace), pass a Subject to get the Question form:
+//	T("core.label.status")              // → "Status:"
+//	T("core.progress.build")            // → "Building..."
+//	T("core.progress.check", "config")  // → "Checking config..."
+//	T("core.count.file", 5)             // → "5 files"
+//	T("core.done.delete", "file")       // → "File deleted"
+//	T("core.fail.delete", "file")       // → "Failed to delete file"
 //
-//	svc.T("core.delete", S("file", "config.yaml")) // "Delete config.yaml?"
+// For semantic intents, pass a Subject:
 //
-// # Fallback Chain
+//	T("core.delete", S("file", "config.yaml")) // → "Delete config.yaml?"
 //
-// When a key is not found, T() tries a fallback chain:
-//  1. Try the exact key in current language
-//  2. Try the exact key in fallback language
-//  3. If key looks like an intent (contains "."), try common.action.{verb}
-//  4. Return the key as-is (or handle according to mode)
+// Use _() for raw key lookup without core.* magic.
 func (s *Service) T(messageID string, args ...any) string {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
 
-	// Check for semantic intent with Subject
-	if strings.HasPrefix(messageID, "core.") && len(args) > 0 {
-		if subject, ok := args[0].(*Subject); ok {
-			// Use C() to resolve the intent, return Question form
-			s.mu.RUnlock()
-			result := s.C(messageID, subject)
-			s.mu.RLock()
-			return result.Question
+	// Handle core.* namespace magic
+	if strings.HasPrefix(messageID, "core.") {
+		if result := s.handleCoreNamespace(messageID, args); result != "" {
+			if s.debug {
+				return debugFormat(messageID, result)
+			}
+			return result
 		}
 	}
 
@@ -669,6 +672,72 @@ func (s *Service) T(messageID string, args ...any) string {
 	return text
 }
 
+// handleCoreNamespace processes core.* namespace patterns.
+// Returns empty string if pattern not recognized.
+// Must be called with s.mu.RLock held.
+func (s *Service) handleCoreNamespace(key string, args []any) string {
+	// core.label.{word} → Label(word)
+	if strings.HasPrefix(key, "core.label.") {
+		word := strings.TrimPrefix(key, "core.label.")
+		return Label(word)
+	}
+
+	// core.progress.{verb} → Progress(verb) or ProgressSubject(verb, subj)
+	if strings.HasPrefix(key, "core.progress.") {
+		verb := strings.TrimPrefix(key, "core.progress.")
+		if len(args) > 0 {
+			if subj, ok := args[0].(string); ok {
+				return ProgressSubject(verb, subj)
+			}
+		}
+		return Progress(verb)
+	}
+
+	// core.count.{noun} → "N noun(s)"
+	if strings.HasPrefix(key, "core.count.") {
+		noun := strings.TrimPrefix(key, "core.count.")
+		if len(args) > 0 {
+			count := toInt(args[0])
+			return fmt.Sprintf("%d %s", count, Pluralize(noun, count))
+		}
+		return noun
+	}
+
+	// core.done.{verb} → ActionResult(verb, subj)
+	if strings.HasPrefix(key, "core.done.") {
+		verb := strings.TrimPrefix(key, "core.done.")
+		if len(args) > 0 {
+			if subj, ok := args[0].(string); ok {
+				return ActionResult(verb, subj)
+			}
+		}
+		return Title(PastTense(verb))
+	}
+
+	// core.fail.{verb} → ActionFailed(verb, subj)
+	if strings.HasPrefix(key, "core.fail.") {
+		verb := strings.TrimPrefix(key, "core.fail.")
+		if len(args) > 0 {
+			if subj, ok := args[0].(string); ok {
+				return ActionFailed(verb, subj)
+			}
+		}
+		return ActionFailed(verb, "")
+	}
+
+	// core.{intent} with Subject → C(intent, subject).Question
+	if len(args) > 0 {
+		if subject, ok := args[0].(*Subject); ok {
+			s.mu.RUnlock()
+			result := s.C(key, subject)
+			s.mu.RLock()
+			return result.Question
+		}
+	}
+
+	return ""
+}
+
 // resolveWithFallback implements the fallback chain for message resolution.
 // Must be called with s.mu.RLock held.
 func (s *Service) resolveWithFallback(messageID string, data any) string {
@@ -856,9 +925,26 @@ func executeIntentTemplate(tmplStr string, data templateData) string {
 	return buf.String()
 }
 
-// _ is the standard gettext-style translation helper. Alias for T().
-func (s *Service) _(messageID string, args ...any) string {
-	return s.T(messageID, args...)
+// Raw is the raw translation helper without core.* namespace magic.
+// Use T() for smart core.* handling, Raw() for direct key lookup.
+func (s *Service) Raw(messageID string, args ...any) string {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	var data any
+	if len(args) > 0 {
+		data = args[0]
+	}
+
+	text := s.resolveWithFallback(messageID, data)
+	if text == "" {
+		return s.handleMissingKey(messageID, args)
+	}
+
+	if s.debug {
+		return debugFormat(messageID, text)
+	}
+	return text
 }
 
 func (s *Service) getMessage(lang, key string) (Message, bool) {