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/components/workspace-card.tsx

@@ -1,5 +1,6 @@
 /** Card component for displaying a workspace. */
 
+import { Link } from "react-router-dom";
 import { Icon } from "./icon";
 import type { Workspace } from "../types/workspace";
 
@@ -27,12 +28,14 @@ export function WorkspaceCard({
 
 	return (
 		<article className={`card workspace-card ${loading ? "loading" : ""}`}>
-			<div className="workspace-header">
-				<h4>{workspace.name}</h4>
-				<span className={`status-badge ${statusClass}`}>
-					{workspace.status}
-				</span>
-			</div>
+			<Link to={`/workspaces/${workspace.id}`} className="workspace-header-link">
+				<div className="workspace-header">
+					<h4>{workspace.name}</h4>
+					<span className={`status-badge ${statusClass}`}>
+						{workspace.status}
+					</span>
+				</div>
+			</Link>
 			<div className="workspace-meta">
 				<p className="workspace-project">
 					{workspace.project_name} / {workspace.repo_name}