feat: walk up directory tree to find .cheat directory (#602)

Previously cheat only checked the current working directory for a .cheat
subdirectory. Now it walks upward through ancestor directories, stopping
at the first .cheat directory found. This mirrors how git discovers .git
directories, so users can place .cheat at their project root and have it
work from any subdirectory.

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

internal/config/config.go

@@ -45,21 +45,20 @@ func New(_ map[string]interface{}, confPath string, resolve bool) (Config, error
 		return Config{}, fmt.Errorf("could not unmarshal yaml: %v", err)
 	}
 
-	// if a .cheat directory exists locally, append it to the cheatpaths
+	// if a .cheat directory exists in the current directory or any ancestor,
+	// append it to the cheatpaths
 	cwd, err := os.Getwd()
 	if err != nil {
 		return Config{}, fmt.Errorf("failed to get cwd: %v", err)
 	}
 
-	local := filepath.Join(cwd, ".cheat")
-	if _, err := os.Stat(local); err == nil {
+	if local := findLocalCheatpath(cwd); local != "" {
 		path := cp.Cheatpath{
 			Name:     "cwd",
 			Path:     local,
 			ReadOnly: false,
 			Tags:     []string{},
 		}
-
 		conf.Cheatpaths = append(conf.Cheatpaths, path)
 	}
 
@@ -140,3 +139,21 @@ func New(_ map[string]interface{}, confPath string, resolve bool) (Config, error
 
 	return conf, nil
 }
+
+// findLocalCheatpath walks upward from dir looking for a .cheat directory.
+// It returns the path to the first .cheat directory found, or an empty string
+// if none exists. This mirrors the discovery pattern used by git for .git
+// directories.
+func findLocalCheatpath(dir string) string {
+	for {
+		candidate := filepath.Join(dir, ".cheat")
+		if info, err := os.Stat(candidate); err == nil && info.IsDir() {
+			return candidate
+		}
+		parent := filepath.Dir(dir)
+		if parent == dir {
+			return ""
+		}
+		dir = parent
+	}
+}