feat(desktop): make the git cockpit work over a remote gateway

After the folder picker fix, an added remote folder was still half-usable:
the desktop's git GUI (coding-rail status, worktree lanes, review pane,
branch switch, file diff) all ran Electron-local git on the USER's machine,
so against a remote-gateway repo they silently degraded to empty.

Mirror the whole surface over the dashboard REST API so it acts on the
BACKEND repo where sessions actually run:

- hermes_cli/web_git.py: git/gh logic (status, worktrees, branches, review
  list/diff/stage/unstage/revert/commit/commit-context/push/ship-info/
  create-pr, file-diff, worktree add/remove, branch switch) shelling to the
  system git, mirroring the Electron ops' shapes.
- web_server.py: /api/git/* routes (same auth gate + _fs_path hardening as
  /api/fs, executor-offloaded, mutations -> 400).
- apps/desktop desktop-git.ts: remote-aware facade exposing the same shape as
  window.hermesDesktop.git; coding-status / review / projects / model /
  desktop-fs route through desktopGit() so local stays Electron, remote hits
  /api/git/*.

Tests: tests/hermes_cli/test_web_server_git.py (real repo: status counts,
review classification, diff incl. untracked all-add, stage+commit roundtrip,
worktree/branch lifecycle, commit-context, gh-absent ship-info, auth) and
desktop-git.test.ts (local vs remote routing, envelope unwrap, POST bodies).

tests/hermes_cli/test_web_server_git.py

@@ -0,0 +1,148 @@
+import subprocess
+from pathlib import Path
+
+import pytest
+
+from hermes_cli import web_server
+
+pytest.importorskip("starlette.testclient")
+from starlette.testclient import TestClient
+
+
+@pytest.fixture
+def client():
+    previous = getattr(web_server.app.state, "auth_required", None)
+    web_server.app.state.auth_required = False
+    test_client = TestClient(web_server.app)
+    test_client.headers[web_server._SESSION_HEADER_NAME] = web_server._SESSION_TOKEN
+    try:
+        yield test_client
+    finally:
+        if previous is None:
+            try:
+                delattr(web_server.app.state, "auth_required")
+            except AttributeError:
+                pass
+        else:
+            web_server.app.state.auth_required = previous
+
+
+def _git(repo: Path, *args: str) -> None:
+    subprocess.run(["git", *args], cwd=repo, check=True, capture_output=True)
+
+
+@pytest.fixture
+def repo(tmp_path):
+    root = tmp_path / "repo"
+    root.mkdir()
+    _git(root, "init", "-q")
+    _git(root, "config", "user.email", "t@example.com")
+    _git(root, "config", "user.name", "Test")
+    (root / "a.txt").write_text("one\ntwo\n")
+    _git(root, "add", "-A")
+    _git(root, "commit", "-qm", "init")
+    # A tracked modification + a brand-new untracked file (the new-file case the
+    # rail/review must surface).
+    (root / "a.txt").write_text("one\ntwo\nthree\n")
+    (root / "new.py").write_text("print(1)\nprint(2)\n")
+    return root
+
+
+def test_status_reports_branch_and_change_counts(client, repo):
+    body = client.get("/api/git/status", params={"path": str(repo)}).json()
+
+    assert body["branch"] == "main"
+    assert body["defaultBranch"] == "main"
+    assert body["detached"] is False
+    # 1 tracked-modified + 1 untracked = 2 changed paths.
+    assert body["changed"] == 2
+    assert body["untracked"] == 1
+    # +1 (a.txt) folded with +2 (untracked new.py) since `git diff HEAD` skips untracked.
+    assert body["added"] == 3
+    assert {f["path"] for f in body["files"]} == {"a.txt", "new.py"}
+
+
+def test_status_returns_null_outside_repo(client, tmp_path):
+    plain = tmp_path / "plain"
+    plain.mkdir()
+
+    assert client.get("/api/git/status", params={"path": str(plain)}).json() is None
+
+
+def test_review_list_classifies_modified_and_untracked(client, repo):
+    body = client.get("/api/git/review/list", params={"path": str(repo)}).json()
+
+    files = {f["path"]: f for f in body["files"]}
+    assert files["a.txt"]["status"] == "M"
+    assert files["a.txt"]["added"] == 1
+    assert files["new.py"]["status"] == "?"
+    assert files["new.py"]["added"] == 2  # untracked insertions counted from disk
+
+
+def test_review_diff_shows_change_and_synthesizes_untracked(client, repo):
+    tracked = client.get(
+        "/api/git/review/diff", params={"path": str(repo), "file": "a.txt"}
+    ).json()["diff"]
+    assert "+three" in tracked
+
+    untracked = client.get(
+        "/api/git/review/diff", params={"path": str(repo), "file": "new.py"}
+    ).json()["diff"]
+    assert "print(1)" in untracked  # all-add diff for a file git doesn't track yet
+
+
+def test_stage_commit_roundtrip_clears_changes(client, repo):
+    assert client.post("/api/git/review/stage", json={"path": str(repo), "file": "a.txt"}).json() == {"ok": True}
+    staged = client.get("/api/git/status", params={"path": str(repo)}).json()
+    assert staged["staged"] >= 1
+
+    assert client.post(
+        "/api/git/review/commit", json={"path": str(repo), "message": "tracked change", "push": False}
+    ).json() == {"ok": True}
+
+    after = client.get("/api/git/status", params={"path": str(repo)}).json()
+    # The tracked change is committed; only the untracked file remains.
+    assert after["changed"] == 1
+    assert after["untracked"] == 1
+
+
+def test_worktrees_and_branch_lifecycle(client, repo):
+    worktrees = client.get("/api/git/worktrees", params={"path": str(repo)}).json()["worktrees"]
+    assert any(tree["isMain"] and tree["path"] == str(repo) for tree in worktrees)
+
+    added = client.post(
+        "/api/git/worktree/add", json={"path": str(repo), "branch": "feature/x"}
+    ).json()
+    assert added["branch"] == "feature/x"
+    assert Path(added["path"]).is_dir()
+
+    branches = client.get("/api/git/branches", params={"path": str(repo)}).json()["branches"]
+    assert any(b["name"] == "feature/x" and b["checkedOut"] for b in branches)
+
+    removed = client.post(
+        "/api/git/worktree/remove", json={"path": str(repo), "worktreePath": added["path"], "force": True}
+    ).json()
+    assert removed["removed"]
+
+
+def test_commit_context_includes_diff_and_untracked(client, repo):
+    body = client.get("/api/git/review/commit-context", params={"path": str(repo)}).json()
+
+    assert "+three" in body["diff"]
+    assert "new.py" in body["diff"]  # untracked files listed since they carry no diff
+
+
+def test_ship_info_degrades_without_gh(client, repo, monkeypatch):
+    monkeypatch.setattr(web_server._web_git.shutil, "which", lambda _name: None)
+
+    assert client.get("/api/git/review/ship-info", params={"path": str(repo)}).json() == {
+        "ghReady": False,
+        "pr": None,
+    }
+
+
+def test_git_endpoints_require_auth(repo):
+    unauth = TestClient(web_server.app)
+
+    assert unauth.get("/api/git/status", params={"path": str(repo)}).status_code == 401
+    assert unauth.post("/api/git/review/stage", json={"path": str(repo)}).status_code == 401