feat(backend): reconcile running bottles' CA on gateway bring-up (0081)

Add `attach_bottled_agents_to_gateway()` as an `@abc.abstractmethod` on
`BottleBackend` and implement the first reconcile step across all three
backends: on a gateway cold boot, replace every already-running agent's
trusted CA with the freshly-minted gateway CA. Reconciling running bottles
is a backend responsibility (only the backend can enumerate its agents and
reach them — firecracker over SSH, docker/macOS over exec/cp), so making it
an abstract method keeps the fix cross-backend by construction.

The gateway rootfs is ephemeral, so a rebuild mints a new CA that every
running bottle distrusts (SSL verification fails — #510). This reconcile is
what distributes the fresh CA, so a routine gateway rebuild now doubles as a
free CA rotation. Per-bottle steps are best-effort: one unreachable or
malformed bottle is logged and skipped, never blocking the others.

Trigger — `Gateway.connect_to_orchestrator` now returns a cold-boot bool
(True when it actually (re)brought the gateway up, False when a healthy
current gateway was left untouched); each infra `ensure_running` gates the
reconcile on it, so it fires exactly on cold boot and never on an adopt.

Git-gate re-provision and egress-token restore fold into this same reconcile
on the same trigger in follow-up PRs (#516).

Refs #516. Addresses #510.

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

bot_bottle/backend/docker/gateway.py

@@ -200,7 +200,7 @@ class DockerGateway(Gateway):
                 f"gateway network {self.network} failed to create: {proc.stderr.strip()}"
             )
 
-    def connect_to_orchestrator(self, orchestrator_url: str, gateway_token: str) -> None:
+    def connect_to_orchestrator(self, orchestrator_url: str, gateway_token: str) -> bool:
         # Bind to this orchestrator (PRD 0070): stash the URL its daemons resolve
         # policy against + the pre-minted `gateway` token they present, then bring
         # the container up. The gateway never mints, so it holds no signing key —
@@ -227,7 +227,7 @@ class DockerGateway(Gateway):
         # just when the container is absent.
         self._ensure_network()
         if self.is_running() and self._running_image_is_current():
-            return
+            return False
         # Clear any stale (stopped OR outdated-image) container holding the
         # fixed name, then start fresh. `rm --force` on an absent name is a
         # tolerated no-op.
@@ -271,6 +271,9 @@ class DockerGateway(Gateway):
         # pre-connect window (they retry /resolve per request).
         if self._control_network:
             self._connect_control_network()
+        # (Re)created a fresh container — signal a cold boot so the caller
+        # reconciles running bottles against it (PRD 0081).
+        return True
 
     def _connect_control_network(self) -> None:
         """Ensure the `--internal` control network exists and attach the gateway