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-s3-handoff.test.js

@@ -98,6 +98,16 @@ describe("a member pane's files live in the member's handoff dir", () => {
     assert.equal(acct?.login, "ah-mia");
   });
 
+  it("refuses a NUL inside a pane's argv or env: it would split the launch file", () => {
+    assert.throws(
+      () => runAs.launchArgv(acct, {}, ["claude", "hi\0--dangerously-skip-permissions"]),
+      {
+        code: "EBADARG",
+      }
+    );
+    assert.throws(() => runAs.launchArgv(acct, { A: "x\0y" }, ["claude"]), { code: "EBADARG" });
+  });
+
   it("copies the context files and writes the prompt there, readable", () => {
     const x = launchExtras(laneId, "claude");
     const ctx = path.join(HANDOFF, `context-${laneId}`);