fix(gitea): handle single-object response in ListContents

When ListContents is called with a path that points to a file (not a
directory), Gitea returns a single JSON object instead of an array.
Previously this caused json.Unmarshal to fail with:
  json: cannot unmarshal object into Go value of type []gitea.ContentEntry

Now ListContents tries array unmarshal first, and falls back to single
object unmarshal, wrapping it in a slice. This allows patterns-files
config to specify individual files like 'README.md' without triggering
a parse error.

Also updates TestGetAllFilesInPath_File to reflect actual Gitea behavior
(single object response, not 404).

Fixes #73

gitea/client.go

@@ -434,6 +434,8 @@ type ContentEntry struct {
 
 // ListContents lists files and directories at a given path in a repo.
 // Pass an empty path to list the repository root.
+// If the path points to a file (not a directory), Gitea returns a single
+// object instead of an array; this method normalizes both cases to a slice.
 func (c *Client) ListContents(ctx context.Context, owner, repo, path string) ([]ContentEntry, error) {
 	// Normalize "." to empty string — Gitea API rejects "." with 500
 	if path == "." {
@@ -451,7 +453,12 @@ func (c *Client) ListContents(ctx context.Context, owner, repo, path string) ([]
 	}
 	var entries []ContentEntry
 	if err := json.Unmarshal(body, &entries); err != nil {
-		return nil, fmt.Errorf("parse contents JSON: %w", err)
+		// Gitea returns a single object (not an array) when path is a file
+		var single ContentEntry
+		if err2 := json.Unmarshal(body, &single); err2 != nil {
+			return nil, fmt.Errorf("parse contents JSON: %w", err)
+		}
+		entries = []ContentEntry{single}
 	}
 	return entries, nil
 }