fix: validate config after PostLoad hooks

Re-run validator after PostLoad, return errors from RootDir, and add Config
alias for C(). Hooks receive *T instead of *Manager.

Co-authored-by: Cursor <cursoragent@cursor.com>

directory.go

@@ -6,47 +6,56 @@ import (
 	"path/filepath"
 )
 
-// RootDir checks the current working directory and its parent directories for
-// a given filename and returns the absolute path to the directory. If the file
-// is not found within the specified depth or any other error occurs, it will
-// panic. If depth is zero or negative, RootDir checks the current directory only.
-func RootDir(searchName string, depth ...int) string {
-	// Get the current working directory
+// RootDir walks from the working directory upward, looking for searchName as a
+// regular file. depth limits how many parent directories are checked (0 = CWD only).
+func RootDir(searchName string, depth ...int) (string, error) {
 	cwd, err := os.Getwd()
 	if err != nil {
-		panic(err)
+		return "", err
 	}
 
-	// Apply default depth if not provided
 	depthVal := 0
 	if len(depth) > 0 {
 		depthVal = depth[0]
 	}
 
-	// Walk directories up to the specified depth to find the file
-	path := walkRootDir(searchName, cwd, depthVal)
+	path, err := walkRootDir(searchName, cwd, depthVal)
+	if err != nil {
+		return "", err
+	}
 	if path == "" {
-		panic(fmt.Errorf("RootDir checked %d directories, no '%s' file found", depthVal+1, searchName))
+		return "", fmt.Errorf("RootDir checked %d directories, no '%s' file found", depthVal+1, searchName)
 	}
 
-	// Try to get the absolute path of the found directory
-	abs, err := filepath.Abs(path)
-	if err != nil || abs == "" {
-		panic(fmt.Errorf("RootDir failed to get absolute path: %v", err))
-	}
-
-	return abs
+	return filepath.Abs(path)
 }
 
-// walkRootDir recursively checks directories up to the specified reverseDepth.
-func walkRootDir(searchName, path string, reverseDepth int) string {
-	if _, err := os.Stat(filepath.Join(path, searchName)); err == nil {
-		return path
+// MustRootDir is like [RootDir] but panics on error.
+func MustRootDir(searchName string, depth ...int) string {
+	dir, err := RootDir(searchName, depth...)
+	if err != nil {
+		panic(err)
+	}
+	return dir
+}
+
+func walkRootDir(searchName, path string, reverseDepth int) (string, error) {
+	candidate := filepath.Join(path, searchName)
+	info, err := os.Stat(candidate)
+	if err == nil {
+		if info.IsDir() {
+			return "", fmt.Errorf("RootDir found directory %q, expected a regular file", candidate)
+		}
+		return path, nil
 	}
 
 	if reverseDepth > 0 {
-		return walkRootDir(searchName, path+"/..", reverseDepth-1)
+		parent := filepath.Dir(path)
+		if parent == path {
+			return "", nil
+		}
+		return walkRootDir(searchName, parent, reverseDepth-1)
 	}
 
-	return ""
+	return "", nil
 }