refactor(orchestrator): rename Sidecar -> Gateway for the consolidated data plane

Retire "sidecar" for the consolidated per-host path (PRD 0070 naming
decision): the orchestrator is the umbrella/control plane, and the
egress/git/supervise data-plane unit it runs is the "gateway".

- git mv sidecar.py -> gateway.py and the two integration + one unit test
  files; DockerSidecar->DockerGateway, Sidecar->Gateway,
  SidecarError->GatewayError, SIDECAR_*->GATEWAY_*, ensure_sidecar->
  ensure_gateway, sidecar_status->gateway_status, container name
  bot-bottle-orch-sidecar->bot-bottle-orch-gateway.
- Prose rename across broker/registry/egress/policy_resolver + PRD 0070.
- Preserved: the image name bot-bottle-sidecars, the
  BOT_BOTTLE_SIDECAR_IMAGE env var, Dockerfile.sidecars, and PRD 0069's
  own stage-name cross-references (that doc still uses "sidecar").

No behavior change. Full unit suite green (1679 tests; the 13
test_sidecar_init /bin/sleep errors are pre-existing NixOS-local noise).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WBMWTEtQdJ4W5UrWuLHCck

bot_bottle/orchestrator/registry.py

@@ -67,9 +67,9 @@ class BottleRecord:
     # Opaque JSON blob for forward-compat (pool slot, ...) — the registry
     # doesn't interpret it, so new fields need no migration.
     metadata: str = ""
-    # The bottle's sidecar policy (opaque JSON — egress allowlist / routes /
+    # The bottle's gateway policy (opaque JSON — egress allowlist / routes /
     # git config). The registry stores and serves it verbatim, keyed by
-    # source IP; the multi-tenant sidecar interprets it.
+    # source IP; the multi-tenant gateway interprets it.
     policy: str = ""
 
     def redacted(self) -> dict[str, object]:
@@ -102,9 +102,9 @@ _MIGRATIONS = TableMigrations(
         # the "one active bottle per source IP" check cheap.
         "CREATE INDEX IF NOT EXISTS idx_orchestrator_bottles_source_ip "
         "ON orchestrator_bottles (source_ip)",
-        # v3 — per-bottle policy (opaque JSON the sidecar interprets): the
+        # v3 — per-bottle policy (opaque JSON the gateway interprets): the
         # egress allowlist / routes / git config selected by source IP. The
-        # multi-tenant sidecar resolves it per request via `attribute`.
+        # multi-tenant gateway resolves it per request via `attribute`.
         "ALTER TABLE orchestrator_bottles ADD COLUMN policy TEXT NOT NULL DEFAULT ''",
     ],
 )
@@ -217,7 +217,7 @@ class RegistryStore(DbStore):
         IP, or None if unknown or ambiguous (more than one — a
         misconfiguration). Safe as the *sole* attributor only where the
         source IP is unspoofable (Firecracker `/31` + nft) and the control
-        plane is reachable only by the trusted sidecar; pair with the
+        plane is reachable only by the trusted gateway; pair with the
         identity token (`attribute`) elsewhere."""
         with self._connect() as conn:
             rows = conn.execute(