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/firecracker/infra.py

@@ -73,7 +73,7 @@ class FirecrackerInfraService(InfraService):
             # The fresh gateway rootfs minted a new CA and lost every bottle's
             # git-gate/token state; reconcile the already-running bottles against
             # it so a gateway rebuild doesn't silently break their egress
-            # (PRD 0081). Cold-boot only — the adopt fast-paths above never reach
+            # (PRD 0083). Cold-boot only — the adopt fast-paths above never reach
             # here, so a healthy current gateway is left untouched.
             if cold_booted:
                 from .backend import FirecrackerBottleBackend

bot_bottle/backend/firecracker/infra_launch.py

@@ -90,7 +90,7 @@ def persist_env_var_secret(private_key: Path, guest_ip: str, secret: str) -> Non
 def attach_ca_to_agent_vm(run_dir: Path, ca_pem: str) -> None:
     """(Re)attach one running agent VM (identified by its `run_dir`) to the
     current gateway: replace its trusted gateway CA with `ca_pem` and rebuild
-    its trust store over SSH (PRD 0081). Unconditional install — there is one
+    its trust store over SSH (PRD 0083). Unconditional install — there is one
     gateway, so no fingerprint match is needed. Bare-pipe input keeps the cert
     off argv.