feat(control-plane): role-scoped signed tokens so the gateway can't drive operator routes

Review follow-up on #469: the data plane held the same control-plane secret
that authorizes every route, so a compromised egress/git-gate could queue a
supervise proposal AND approve it (or rewrite policy, read injected tokens) —
the (source_ip, identity_token) checks attribute the *bottle*, not the caller.

Replace the single shared bearer secret with role-scoped, HMAC-signed tokens
(compact HS256 JWTs, stdlib-only — no new dependency):

  * new `control_auth` mints/verifies `{role}` tokens; roles are `gateway`
    (data plane) and `cli` (host operator/launcher).
  * the orchestrator holds only the signing *key* and verifies; `dispatch`
    gates each route by role — `gateway` reaches /resolve + /supervise/
    {propose,poll}, everything else is `cli`-only (401 unauthenticated,
    403 wrong role).
  * the gateway is handed a pre-minted `gateway` token it cannot rewrite into
    `cli`; the host CLI mints its own `cli` token from the host key.
  * `gateway_init` scopes the signing key to the orchestrator process and the
    gateway token to the data-plane daemons, so even in the combined infra
    container a compromised data-plane daemon never sees the key.

Launchers (docker gateway + infra, macOS infra) inject the minted token(s);
Firecracker stays open behind its nft boundary. Open mode (no key) still grants
full `cli` access — the fail-visible fallback for tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_orchestrator_client.py

@@ -7,15 +7,30 @@ import unittest
 import urllib.error
 from unittest.mock import MagicMock, patch
 
+from bot_bottle.control_auth import ROLE_CLI, verify
 from bot_bottle.orchestrator.client import (
     OrchestratorClient,
     OrchestratorClientError,
     RegisteredBottle,
+    _host_auth_token,
 )
 
 _URLOPEN = "bot_bottle.orchestrator.client.urllib.request.urlopen"
 
 
+class TestHostAuthToken(unittest.TestCase):
+    def test_mints_a_cli_token_from_the_host_key(self) -> None:
+        with patch("bot_bottle.orchestrator.client.host_control_plane_token",
+                   return_value="signing-key"):
+            tok = _host_auth_token()
+        self.assertEqual(ROLE_CLI, verify(tok, "signing-key"))
+
+    def test_returns_empty_when_key_unreadable(self) -> None:
+        with patch("bot_bottle.orchestrator.client.host_control_plane_token",
+                   side_effect=OSError("no host root")):
+            self.assertEqual("", _host_auth_token())
+
+
 def _resp(status: int, payload: object) -> MagicMock:
     m = MagicMock()
     inner = m.__enter__.return_value