feat(tui): port classic CLI /reload (.env hot-reload) to TUI

Classic CLI exposes ``/reload`` (re-reads ~/.hermes/.env into
``os.environ`` via ``hermes_cli.config.reload_env``) so newly added API
keys take effect without restarting the session.  The TUI was missing
the parity command, so users had to Ctrl+C out and ``hermes --tui``
again whenever they added or rotated a credential.

Three small wires:

* New ``reload.env`` JSON-RPC method in ``tui_gateway/server.py`` that
  delegates to ``hermes_cli.config.reload_env`` and returns the count
  of vars updated.
* New ``/reload`` slash command in ``ui-tui/src/app/slash/commands/ops.ts``
  matching the existing ``/reload-mcp`` pattern (native RPC, no slash
  worker).
* Drop ``cli_only=True`` from the ``reload`` ``CommandDef`` in
  ``hermes_cli/commands.py`` so help/menus surface it in the TUI too.
  ``reload_env`` itself is environment-agnostic.

Same caveat as classic CLI: the *currently constructed* agent's
credential pool / provider routing does not auto-rebuild.  Users who
want a brand-new credential resolution should follow with ``/new``.

Tests:
* New ``test_reload_env_rpc_calls_hermes_cli_reload_env`` confirms
  RPC delegates and reports the count.
* New ``test_reload_env_rpc_surfaces_errors`` confirms exceptions are
  rendered as JSON-RPC errors.
* ``createSlashHandler.test.ts`` slash-parity matrix extended with
  ``['/reload', 'reload.env', {}]`` so we can't regress the routing.

Validation:
  scripts/run_tests.sh tests/test_tui_gateway_server.py — 92/92.
  scripts/run_tests.sh tests/hermes_cli/test_commands.py — 128/128.
  cd ui-tui && npm run type-check — clean; npm test --run — 390/390.

tests/test_tui_gateway_server.py

@@ -3448,3 +3448,39 @@ def test_config_set_indicator_none_keeps_blank_repr(monkeypatch):
     )
     assert "error" in resp
     assert "unknown indicator: ''" in resp["error"]["message"]
+
+
+# ── reload.env ───────────────────────────────────────────────────────
+
+
+def test_reload_env_rpc_calls_hermes_cli_reload_env(monkeypatch):
+    """reload.env mirrors classic CLI's `/reload` — re-reads ~/.hermes/.env
+    into the gateway process and reports the count of vars updated."""
+    calls = {"n": 0}
+
+    def _fake_reload():
+        calls["n"] += 1
+        return 7
+
+    fake = types.SimpleNamespace(reload_env=_fake_reload)
+    with patch.dict(sys.modules, {"hermes_cli.config": fake}):
+        resp = server.handle_request(
+            {"id": "1", "method": "reload.env", "params": {}}
+        )
+
+    assert resp["result"] == {"updated": 7}
+    assert calls["n"] == 1
+
+
+def test_reload_env_rpc_surfaces_errors(monkeypatch):
+    def _broken():
+        raise RuntimeError("env path locked")
+
+    fake = types.SimpleNamespace(reload_env=_broken)
+    with patch.dict(sys.modules, {"hermes_cli.config": fake}):
+        resp = server.handle_request(
+            {"id": "1", "method": "reload.env", "params": {}}
+        )
+
+    assert "error" in resp
+    assert "env path locked" in resp["error"]["message"]