docs: renumber PRD 0081 -> 0083 across the reconcile chunk

Follows the base PR's renumber (0081 was already taken; main is on 0082). Update
every `PRD 0081` reference in the gateway-attach code, tests, and ADR 0006, plus
ADR 0006's link to the PRD file. No behaviour change.

Refs #516, #519.

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

bot_bottle/backend/docker/infra_launch.py

@@ -83,7 +83,7 @@ def running_agent_containers(
 ) -> list[str]:
     """Every running agent container on the gateway `network` (the gateway
     itself excluded) — the bottles the bring-up reconcile attaches to the fresh
-    gateway (PRD 0081). Raises `OSError` if `docker` can't be run (fail hard: a
+    gateway (PRD 0083). Raises `OSError` if `docker` can't be run (fail hard: a
     reconcile that can't list its bottles must not look like "no bottles")."""
     proc = run_docker([
         "docker", "network", "inspect", "--format",
@@ -98,7 +98,7 @@ def running_agent_containers(
 def push_ca_to_container(container: str, ca_pem: str) -> None:
     """(Re)attach one running agent container to the current gateway: replace
     its trusted gateway CA with `ca_pem` and rebuild its trust store via
-    `docker cp` + `docker exec` (PRD 0081). Unconditional install — there is one
+    `docker cp` + `docker exec` (PRD 0083). Unconditional install — there is one
     gateway, so no fingerprint match is needed.
 
     Fail hard: raises `InfraLaunchError` (naming the container) on any failure —