chore: housekeeping and refactoring (bump to 4.7.1)

- Remove unused parameters, dead files, and inaccurate doc.go files
- Extract shared helpers, eliminate duplication
- Rename cheatpath.Cheatpath to cheatpath.Path
- Optimize filesystem walks (WalkDir, skip .git)
- Move sheet name validation to sheet.Validate
- Move integration tests to test/integration/
- Consolidate internal/mock into mocks/
- Move fuzz.sh to test/
- Inline loadSheets helper into command callers
- Extract config.New into its own file
- Fix stale references in HACKING.md and CLAUDE.md
- Restore plan9 build target
- Remove redundant and low-value tests
- Clean up project documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/display/faint.go

@@ -2,17 +2,13 @@
 // cheatsheet content to stdout, or alternatively the system pager.
 package display
 
-import (
-	"fmt"
-
-	"github.com/cheat/cheat/internal/config"
-)
+import "fmt"
 
 // Faint returns a faintly-colored string that's used to de-prioritize text
 // written to stdout
-func Faint(str string, conf config.Config) string {
+func Faint(str string, colorize bool) string {
 	// make `str` faint only if colorization has been requested
-	if conf.Colorize {
+	if colorize {
 		return fmt.Sprintf("\033[2m%s\033[0m", str)
 	}