AUD-56: deploy prep - token script, container user fix, runbook

- Add scripts/provision-hub-tokens.sh. It adds the five HUB_TOKEN_* keys to
  ~/.config/environment.d/10-secrets.conf. It is idempotent, keeps mode 600,
  leaves a mode-600 backup, and never prints a value. It uses openssl when
  present and /dev/urandom otherwise (this host has no openssl).
- docker-compose.yml: run the container as the host user. The image's
  distroless nonroot user cannot read the 0600 secrets file. With nonroot the
  Hub read no tokens and every /ask returned 401.
- Document the deploy steps, the finding, and the dry-run evidence in
  docs/outline/04-agent-runbook.md, docs/outline/02-config-and-env.md, README.md.

Dry run on port 18788 with a scratch secrets file: /health ok with
omniroute ok, control action refused, bad token 401. The host secrets file and
the running hub container were not touched.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

docker-compose.yml

@@ -6,6 +6,10 @@ services:
     image: central-ai-hub:local
     container_name: hub
     restart: unless-stopped
+    # The secrets file is bind-mounted read-only with mode 0600, owned by the
+    # host user. The image's distroless nonroot user (65532) cannot read it, so
+    # the container runs as the host user instead. No host file change needed.
+    user: "${HUB_UID:-1000}:${HUB_GID:-100}"
     ports:
       - "8788:8788"
     environment: