feat(cli): add core go cov command

- Add `core go cov` for coverage reports
- Generate HTML report with --html
- Open in browser with --open
- Fail on threshold with --threshold 80
- Colour-coded coverage output
- Update SKILL.md documentation

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

.claude/skills/core/SKILL.md

@@ -14,7 +14,7 @@ The `core` command provides a unified interface for Go/Wails development, multi-
 | Task | Command | Notes |
 |------|---------|-------|
 | Run Go tests | `core go test` | Sets macOS deployment target, filters warnings |
-| Run Go tests with coverage | `core go test --coverage` | Per-package breakdown |
+| Run Go tests with coverage | `core go cov` | HTML report, thresholds |
 | Format Go code | `core go fmt --fix` | Uses goimports/gofmt |
 | Lint Go code | `core go lint` | Uses golangci-lint |
 | Tidy Go modules | `core go mod tidy` | go mod tidy wrapper |
@@ -233,8 +233,8 @@ core pkg outdated
 
 | Task | Command | Notes |
 |------|---------|-------|
-| Run tests | `core go test` | CGO_ENABLED=0, filters warnings |
-| Run tests with coverage | `core go test --coverage` | Per-package breakdown |
+| Run tests | `core go test` | Filters warnings, colour output |
+| Coverage report | `core go cov` | HTML report, thresholds |
 | Format code | `core go fmt --fix` | Uses goimports if available |
 | Lint code | `core go lint` | Uses golangci-lint |
 | Install binary | `core go install` | Auto-detects cmd/, --no-cgo option |
@@ -257,6 +257,25 @@ core go install --no-cgo
 core go install -v
 ```
 
+### Coverage
+
+```bash
+# Run tests with coverage summary
+core go cov
+
+# Generate HTML report
+core go cov --html
+
+# Generate and open in browser
+core go cov --open
+
+# Fail if coverage below threshold
+core go cov --threshold 80
+
+# Specific package
+core go cov --pkg ./pkg/release
+```
+
 ### Testing
 
 ```bash

cmd/core/cmd/go.go

@@ -17,14 +17,16 @@ func AddGoCommands(parent *clir.Cli) {
 	goCmd := parent.NewSubCommand("go", "Go development tools")
 	goCmd.LongDescription("Go development tools with enhanced output and environment setup.\n\n" +
 		"Commands:\n" +
-		"  test     Run tests with coverage\n" +
+		"  test     Run tests\n" +
+		"  cov      Run tests with coverage report\n" +
 		"  fmt      Format Go code\n" +
 		"  lint     Run golangci-lint\n" +
-		"  install  Install Go binary (CGO_ENABLED=0)\n" +
+		"  install  Install Go binary\n" +
 		"  mod      Module management (tidy, download, verify)\n" +
 		"  work     Workspace management")
 
 	addGoTestCommand(goCmd)
+	addGoCovCommand(goCmd)
 	addGoFmtCommand(goCmd)
 	addGoLintCommand(goCmd)
 	addGoInstallCommand(goCmd)
@@ -186,6 +188,131 @@ func parseOverallCoverage(output string) float64 {
 	return total / float64(len(matches))
 }
 
+func addGoCovCommand(parent *clir.Command) {
+	var (
+		pkg     string
+		html    bool
+		open    bool
+		threshold float64
+	)
+
+	covCmd := parent.NewSubCommand("cov", "Run tests with coverage report")
+	covCmd.LongDescription("Run tests and generate coverage report.\n\n" +
+		"Examples:\n" +
+		"  core go cov                  # Run with coverage summary\n" +
+		"  core go cov --html           # Generate HTML report\n" +
+		"  core go cov --open           # Generate and open HTML report\n" +
+		"  core go cov --threshold 80   # Fail if coverage < 80%")
+
+	covCmd.StringFlag("pkg", "Package to test (default: ./...)", &pkg)
+	covCmd.BoolFlag("html", "Generate HTML coverage report", &html)
+	covCmd.BoolFlag("open", "Generate and open HTML report in browser", &open)
+	covCmd.Float64Flag("threshold", "Minimum coverage percentage (exit 1 if below)", &threshold)
+
+	covCmd.Action(func() error {
+		if pkg == "" {
+			pkg = "./..."
+		}
+
+		// Create temp file for coverage data
+		covFile, err := os.CreateTemp("", "coverage-*.out")
+		if err != nil {
+			return fmt.Errorf("failed to create coverage file: %w", err)
+		}
+		covPath := covFile.Name()
+		covFile.Close()
+		defer os.Remove(covPath)
+
+		fmt.Printf("%s Running tests with coverage\n", dimStyle.Render("Coverage:"))
+		fmt.Printf("  %s %s\n", dimStyle.Render("Package:"), pkg)
+		fmt.Println()
+
+		// Run tests with coverage
+		args := []string{"test", "-coverprofile=" + covPath, "-covermode=atomic", pkg}
+		cmd := exec.Command("go", args...)
+		cmd.Env = append(os.Environ(), "MACOSX_DEPLOYMENT_TARGET=26.0")
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+
+		testErr := cmd.Run()
+
+		// Get coverage percentage
+		covCmd := exec.Command("go", "tool", "cover", "-func="+covPath)
+		covOutput, err := covCmd.Output()
+		if err != nil {
+			if testErr != nil {
+				return testErr
+			}
+			return fmt.Errorf("failed to get coverage: %w", err)
+		}
+
+		// Parse total coverage from last line
+		lines := strings.Split(strings.TrimSpace(string(covOutput)), "\n")
+		var totalCov float64
+		if len(lines) > 0 {
+			lastLine := lines[len(lines)-1]
+			// Format: "total:    (statements)    XX.X%"
+			if strings.Contains(lastLine, "total:") {
+				parts := strings.Fields(lastLine)
+				if len(parts) >= 3 {
+					covStr := strings.TrimSuffix(parts[len(parts)-1], "%")
+					fmt.Sscanf(covStr, "%f", &totalCov)
+				}
+			}
+		}
+
+		// Print coverage summary
+		fmt.Println()
+		covStyle := successStyle
+		if totalCov < 50 {
+			covStyle = errorStyle
+		} else if totalCov < 80 {
+			covStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#f59e0b"))
+		}
+		fmt.Printf("  %s %s\n", dimStyle.Render("Total:"), covStyle.Render(fmt.Sprintf("%.1f%%", totalCov)))
+
+		// Generate HTML if requested
+		if html || open {
+			htmlPath := "coverage.html"
+			htmlCmd := exec.Command("go", "tool", "cover", "-html="+covPath, "-o="+htmlPath)
+			if err := htmlCmd.Run(); err != nil {
+				return fmt.Errorf("failed to generate HTML: %w", err)
+			}
+			fmt.Printf("  %s %s\n", dimStyle.Render("HTML:"), htmlPath)
+
+			if open {
+				// Open in browser
+				var openCmd *exec.Cmd
+				switch {
+				case exec.Command("which", "open").Run() == nil:
+					openCmd = exec.Command("open", htmlPath)
+				case exec.Command("which", "xdg-open").Run() == nil:
+					openCmd = exec.Command("xdg-open", htmlPath)
+				default:
+					fmt.Printf("  %s\n", dimStyle.Render("(open manually)"))
+				}
+				if openCmd != nil {
+					openCmd.Run()
+				}
+			}
+		}
+
+		// Check threshold
+		if threshold > 0 && totalCov < threshold {
+			fmt.Printf("\n%s Coverage %.1f%% is below threshold %.1f%%\n",
+				errorStyle.Render("FAIL"), totalCov, threshold)
+			return fmt.Errorf("coverage below threshold")
+		}
+
+		if testErr != nil {
+			return testErr
+		}
+
+		fmt.Printf("\n%s\n", successStyle.Render("OK"))
+		return nil
+	})
+}
+
 func addGoFmtCommand(parent *clir.Command) {
 	var (
 		fix   bool