feat(git): /git overview page and diff viewer

Add git module with repo status overview (/git) and per-repo detail page
(/git/[repo]) featuring a color-coded diff viewer (+ green, - red).
Reads repo paths from REPO_PATHS env var, calls ops-agent git_status and
git_diff commands. Status badges: clean (green), dirty (orange),
behind-origin (blue).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/git/[repo]/page.tsx

@@ -0,0 +1,89 @@
+import Link from 'next/link'
+import { redirect } from 'next/navigation'
+import { getCurrentUser } from '@/lib/session'
+import { execAgent } from '@/lib/agent-client'
+import { parseGitStatus } from '@/lib/parse-git'
+import DiffViewer from './_components/diff-viewer'
+
+export const dynamic = 'force-dynamic'
+
+type Props = {
+  params: Promise<{ repo: string }>
+}
+
+function findRepoPath(repoName: string): string | null {
+  const paths = (process.env.REPO_PATHS ?? '')
+    .split(',')
+    .map((p) => p.trim())
+    .filter(Boolean)
+  return paths.find((p) => p.split('/').filter(Boolean).pop() === repoName) ?? null
+}
+
+export default async function GitRepoPage({ params }: Props) {
+  const user = await getCurrentUser()
+  if (!user) redirect('/login')
+
+  const { repo } = await params
+  const repoName = decodeURIComponent(repo)
+  const repoPath = findRepoPath(repoName)
+
+  if (!repoPath) {
+    return (
+      <div className="min-h-screen bg-background p-6">
+        <div className="mx-auto max-w-6xl space-y-6">
+          <div className="flex items-center gap-3">
+            <Link href="/git" className="text-sm text-muted-foreground hover:text-foreground">
+              ← Repositories
+            </Link>
+          </div>
+          <div className="rounded-lg border border-destructive/30 bg-destructive/10 px-4 py-3 text-sm text-destructive">
+            Repo &quot;{repoName}&quot; not found in REPO_PATHS.
+          </div>
+        </div>
+      </div>
+    )
+  }
+
+  let statusSummary = ''
+  let initialDiff = ''
+  let initialError: string | null = null
+
+  try {
+    const [statusOut, diffOut] = await Promise.all([
+      execAgent('git_status', [repoPath]),
+      execAgent('git_diff', [repoPath]),
+    ])
+    const status = parseGitStatus(statusOut)
+    statusSummary = `${status.branch}${status.dirty ? ' · dirty' : ' · clean'}${status.ahead ? ` · ↑${status.ahead} ahead` : ''}${status.behind ? ` · ↓${status.behind} behind` : ''}`
+    initialDiff = diffOut
+  } catch (err) {
+    initialError = err instanceof Error ? err.message : 'Failed to fetch repo data'
+  }
+
+  return (
+    <div className="min-h-screen bg-background p-6">
+      <div className="mx-auto max-w-6xl space-y-6">
+        <div className="flex items-center gap-3">
+          <Link href="/git" className="text-sm text-muted-foreground hover:text-foreground">
+            ← Repositories
+          </Link>
+          <span className="text-muted-foreground">/</span>
+          <h1 className="text-2xl font-semibold tracking-tight font-mono">{repoName}</h1>
+        </div>
+
+        {statusSummary && (
+          <div className="flex items-center gap-2 text-sm text-muted-foreground font-mono">
+            <span>{repoPath}</span>
+            <span className="text-border">·</span>
+            <span>{statusSummary}</span>
+          </div>
+        )}
+
+        <div>
+          <h2 className="text-base font-semibold mb-3">Uncommitted changes</h2>
+          <DiffViewer repoPath={repoPath} initialDiff={initialDiff} initialError={initialError} />
+        </div>
+      </div>
+    </div>
+  )
+}