feat: live deployment with automated acceptance checklist (phase 13)

- APP_INTERNAL_URL: in-network base URL for §5.2 callbacks and signed
  attachment URLs handed to the external services (compose: http://app:8787)
- work-performer image runs as the node user with ~/.claude mounted into
  /home/node — the claude CLI refuses --dangerously-skip-permissions as root
- scripts/acceptance.sh: re-run-safe live verification of the §13 checklist
  (demo import within one poll, subdivide sum=1 + editable, extend sibling,
  publish/bounty math, decline/claim/approve, changes-requested loop,
  approval award in metrics, unassign, AI job through real Claude Code with
  signed idempotent callback, breaker independence between the two services)
- README/DECISIONS: sudo HOME gotcha, internal URL, non-root performer

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

services/work-performer/Dockerfile

@@ -4,6 +4,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends git ca-certific
     && npm install -g @anthropic-ai/claude-code
 WORKDIR /srv
 COPY server.js .
-RUN mkdir -p /work
+# claude refuses --dangerously-skip-permissions as root: run as the node
+# user (uid 1000, matches typical host ownership of the mounted ~/.claude)
+RUN mkdir -p /work && chown node:node /work /srv
+USER node
+ENV HOME=/home/node
 EXPOSE 8091
 CMD ["node", "server.js"]