feat: workspace-first UI refresh - PR-2 workspace detail page

- Add workspace detail page (/workspaces/:id) with 4 tabs:
  - Files: file tree, viewer, editor, git toolbar (commit/push/pull/fetch)
  - Git: branch selector, commit history
  - Tools: instance grid, start tool modal
  - Settings: workspace info read-only
- Add workspace API clients: workspace-files, workspace-git, workspace-instances
- Add hooks: useWorkspaceFiles, useWorkspaceGit, useWorkspaceInstances
- WorkspaceCard links to detail page via router Link
- Add comprehensive CSS for workspace detail layout
- Mobile: bottom tab bar, responsive file tree/split
- TypeScript + eslint clean

Quality gates: tsc --noEmit clean, eslint clean

apps/web/src/router.tsx

@@ -17,6 +17,7 @@ import { SSHKeysPage } from "./pages/ssh-keys";
 import { ConfigProfilesPage } from "./pages/config-profiles";
 import { SessionsPage } from "./pages/sessions";
 import { WorkspacesPage } from "./pages/workspaces";
+import { WorkspaceDetailPage } from "./pages/workspace-detail";
 
 export const AppRouter = () => {
 	return (
@@ -59,6 +60,7 @@ export const AppRouter = () => {
 				</Route>
 				<Route path="sessions" element={<SessionsPage />} />
 				<Route path="workspaces" element={<WorkspacesPage />} />
+				<Route path="workspaces/:workspaceId" element={<WorkspaceDetailPage />} />
 				<Route path="tool-workshop" element={<ToolWorkshopPage />} />
 				<Route
 					path="instances/:instanceId/terminal"