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>

cmd/app/main.go

@@ -109,7 +109,7 @@ func run() error {
 
 	// Background job queue + atomization handlers.
 	runner := jobs.NewRunner(st, log, reg, 4)
-	atomSvc := atomize.NewService(st, atomClient, log, cfg.AppBaseURL,
+	atomSvc := atomize.NewService(st, atomClient, log, cfg.AppInternalURL,
 		[]byte(cfg.SessionSecret), srv.Publish)
 	runner.Register(atomize.JobKindSubdivide, atomSvc.HandleSubdivide)
 	runner.Register(atomize.JobKindExtend, atomSvc.HandleExtend)