feat(prd-0081): reprovision CA, git-gate, and egress tokens on gateway bring-up

On a Firecracker gateway cold boot, reconcile every live agent VM against
the fresh gateway: push the new mitmproxy CA into each agent's trust store,
re-provision git-gate repos/creds from the persisted upstreams snapshot,
and restore egress tokens. Per-bottle failures are logged and skipped so
one unreachable VM does not block the rest.

New modules / changes:
- backend/firecracker/reconcile.py: attach_bottled_agents_to_gateway,
  _push_ca, _reprovision_git_gate, _guest_ip_from_config
- git_gate/provision.py: write upstreams.json after key provisioning so
  the bring-up reconcile can reconstruct the upstream table without the
  manifest
- backend/firecracker/infra.py: call attach_bottled_agents_to_gateway in
  the cold-boot branch of ensure_running()
- backend/base.py: no-op default on BottleBackend
- backend/firecracker/consolidated_launch.py: remove superseded
  _reprovision_running_bottles / _guest_ip_from_config
- orchestrator: OrchestratorCore.update_agent_secret + POST
  /bottles/<id>/secret + client.update_agent_secret (single-secret
  in-place update, the reusable primitive from the 2026-07-26 hotfix)
- tests: 15 new tests in test_firecracker_reconcile.py; updated
  test_firecracker_infra.py cold-boot cases; stale FC reprovision tests
  removed from test_backend_secret_reprovision.py

Closes #516.

setup.py

@@ -10,8 +10,6 @@ Kept in sync with ``bot_bottle.resources.BUNDLED_RESOURCES`` — the
 
 from __future__ import annotations
 
-import json
-import os
 import shutil
 from pathlib import Path
 
@@ -46,18 +44,6 @@ class _BundleResources(build_py):
             dst = pkg_resources / rel
             dst.parent.mkdir(parents=True, exist_ok=True)
             shutil.copy2(src, dst)
-        manifest_dest = Path(self.build_lib) / "bot_bottle" / "release-manifest.json"
-        manifest_input = os.environ.get("BOT_BOTTLE_RELEASE_MANIFEST", "").strip()
-        if manifest_input:
-            shutil.copy2(manifest_input, manifest_dest)
-        else:
-            # Wheels built ad hoc retain the contributor/install.sh local-build
-            # behavior. The release workflow always replaces this marker with
-            # validated immutable artifact identities.
-            manifest_dest.write_text(
-                json.dumps({"schema": 1, "development": True}) + "\n",
-                encoding="utf-8",
-            )
 
 
 setup(cmdclass={"build_py": _BundleResources})