fix: enable folder navigation in workspace file browser

FilesTab in WorkspaceDetailPage was returning early for directories with
no action, making folders unclickable.

Changes:
- use-workspace-files.ts: add currentPath state and navigateTo() function;
  refresh() now passes currentPath to listWorkspaceFiles API
- WorkspaceDetailPage.tsx FilesTab: handleSelect now calls navigateTo()
  for directories; added navigateUp() button using '..' when not at root
- Clear selected file/editor state when changing directories

Quality gates: tsc --noEmit pass, npm run build pass, 82/82 tests pass

apps/web/src/hooks/use-workspace-files.ts

@@ -11,11 +11,13 @@ import {
 export interface UseWorkspaceFilesResult {
 	entries: FileEntry[];
 	content: string | null;
+	currentPath: string;
 	loading: boolean;
 	error: string | null;
 	refresh: () => Promise<void>;
 	loadFile: (path: string) => Promise<void>;
 	saveFile: (path: string, content: string, message?: string) => Promise<void>;
+	navigateTo: (path: string) => void;
 }
 
 export function useWorkspaceFiles(
@@ -23,6 +25,7 @@ export function useWorkspaceFiles(
 ): UseWorkspaceFilesResult {
 	const [entries, setEntries] = useState<FileEntry[]>([]);
 	const [content, setContent] = useState<string | null>(null);
+	const [currentPath, setCurrentPath] = useState("");
 	const [loading, setLoading] = useState(true);
 	const [error, setError] = useState<string | null>(null);
 
@@ -30,14 +33,19 @@ export function useWorkspaceFiles(
 		setLoading(true);
 		setError(null);
 		try {
-			const data = await listWorkspaceFiles(workspaceId);
+			const data = await listWorkspaceFiles(workspaceId, currentPath);
 			setEntries(data);
 		} catch (err) {
 			setError(err instanceof Error ? err.message : "Failed to load files");
 		} finally {
 			setLoading(false);
 		}
-	}, [workspaceId]);
+	}, [workspaceId, currentPath]);
+
+	const navigateTo = useCallback((path: string) => {
+		setCurrentPath(path);
+		setContent(null);
+	}, []);
 
 	const loadFile = useCallback(
 		async (path: string) => {
@@ -64,5 +72,5 @@ export function useWorkspaceFiles(
 		refresh();
 	}, [refresh]);
 
-	return { entries, content, loading, error, refresh, loadFile, saveFile };
+	return { entries, content, currentPath, loading, error, refresh, loadFile, saveFile, navigateTo };
 }

apps/web/src/pages/WorkspaceDetailPage.tsx

@@ -150,7 +150,7 @@ function MobileTabBar({
 /* ─── Files Tab ─── */
 
 function FilesTab({ workspaceId }: { workspaceId: string }) {
-	const { entries, content, loadFile, saveFile, loading, error } =
+	const { entries, content, currentPath, loadFile, saveFile, loading, error, navigateTo } =
 		useWorkspaceFiles(workspaceId);
 	const { status, commit, push, pull, fetch } = useWorkspaceGit(workspaceId);
 	const [selectedPath, setSelectedPath] = useState<string | null>(null);
@@ -159,13 +159,28 @@ function FilesTab({ workspaceId }: { workspaceId: string }) {
 	const [commitMessage, setCommitMessage] = useState("");
 
 	const handleSelect = (entry: FileEntry) => {
-		if (entry.type === "directory") return;
+		if (entry.type === "directory") {
+			setSelectedPath(null);
+			setIsEditing(false);
+			setEditContent(null);
+			navigateTo(entry.path);
+			return;
+		}
 		setSelectedPath(entry.path);
 		setIsEditing(false);
 		setEditContent(null);
 		loadFile(entry.path);
 	};
 
+	const navigateUp = () => {
+		if (!currentPath) return;
+		const parentPath = currentPath.split("/").slice(0, -1).join("/");
+		navigateTo(parentPath);
+		setSelectedPath(null);
+		setIsEditing(false);
+		setEditContent(null);
+	};
+
 	const handleEdit = () => {
 		if (content !== null) {
 			setEditContent(content);
@@ -224,6 +239,15 @@ function FilesTab({ workspaceId }: { workspaceId: string }) {
 			)}
 			<div className="files-split">
 				<div className="file-tree">
+					{currentPath && (
+						<button
+							className="tree-entry tree-up"
+							onClick={navigateUp}
+							type="button"
+						>
+							<Icon name="folder" size="sm" /> ..
+						</button>
+					)}
 					{loading && <p className="muted">Loading...</p>}
 					{error && <p className="error-text">{error}</p>}
 					{entries.map((entry) => (