feat: v2.7.7 — File Explorer on workspaces and the user's home, clone with per-user git identity

- File Explorer (Files in the sidebar, /files; also from a workspace's Files
  tab, portalled so no panel clips it), laid out like GNOME Files: places
  (Home, workspaces, Trash), Back/Forward/Up, path bar, search, icon grid with
  image thumbnails or list, labelled New/Upload, selection action bar, hidden
  files behind Ctrl+H, right-click menus and the usual keys.
  Make, rename, move, copy (within a workspace, between workspaces, home ↔
  workspace), delete into a per-account trash restorable for 7 days, streamed
  upload of files and whole folders (≤ 500 MB a batch, Replace / Keep both /
  Skip on a taken name), download a file or a zip of anything.
  server/lib/file-explorer.js, /api/lanes/:id/fs/*, /api/homes/:who/fs/*.
- The user's home: every dot entry at its top stays hidden and refused
  (also via a symlink, download, zip or as a copy source); an admin may view
  other users' homes read-only, audited.
- write-as learns move/copy (re-run `sudo agenthub server install-system`).
- Hardening: a write to a workspace re-checks its owner by the live role;
  S3 keeps its server.conf if the file stops reading and a tmux call never
  falls back to the host's server; the AI Proxy gateway marks what it relays
  and the dashboard refuses it; a NUL in a pane's argv/env is refused.
- OpenAPI for the new routes (server/openapi-extra/files.js); docs (API,
  SERVER-MODE, CLAUDE.md) updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/__tests__/server-mode-proxy-gateway.test.js

@@ -202,6 +202,24 @@ describe("the proxy gateway", () => {
     assert.equal(res.status, 403);
   });
 
+  it("marks what it relays, and the dashboard refuses anything so marked", async () => {
+    seen = [];
+    await gw(`${profileName}/v1/messages`, { headers: { "x-api-key": LIVE_TOKEN }, body: "{}" });
+    assert.equal(seen[0].headers["x-agenthub-via-gateway"], "1");
+    // A profile pointed back at the dashboard itself: what arrives carries
+    // the mark, so no route answers it — the hooks least of all.
+    const self = `http://127.0.0.1:${server.address().port}`;
+    for (const p of ["/api/hooks/event", "/api/lanes", "/api/health"]) {
+      const r = await fetch(`${self}${p}`, {
+        method: "POST",
+        headers: { "content-type": "application/json", "x-agenthub-via-gateway": "1" },
+        body: "{}",
+      });
+      assert.equal(r.status, 403, p);
+      assert.equal((await r.json()).error.code, "EGATEWAY");
+    }
+  });
+
   it("is not there in local mode", async () => {
     delete process.env.AGENTHUB_MODE;
     try {