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/gateway/__init__.py

@@ -122,12 +122,18 @@ class Gateway(abc.ABC):
         return
 
     @abc.abstractmethod
-    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 the gateway to this orchestrator and bring it up: store the URL +
         the pre-minted `gateway` token as instance state, then (re)start the
         gateway unit carrying the mitmproxy CA + that token, resolving policy
         against `orchestrator_url`. Idempotent — a healthy, current gateway on
-        the same binding is left alone; a changed binding reconciles it."""
+        the same binding is left alone; a changed binding reconciles it.
+
+        Returns True when the gateway was actually (re)brought up (a cold boot,
+        so its mitmproxy minted a fresh CA and lost its per-bottle state), False
+        when a healthy current gateway was left untouched. The bring-up flow
+        uses this as the cold-boot signal that gates the running-bottle
+        reconcile (`attach_bottled_agents_to_gateway`, PRD 0081)."""
 
     @abc.abstractmethod
     def is_running(self) -> bool: