orchestration: run workers as a sprite service; record wave 4 completion

setsid nohup did not survive orchestrator teardown on 09-06 (uptime was
continuous, so this was a teardown kill, not the hazard-#5 suspend).
tasks/service-worker.sh runs a worker under the sprite service supervisor
instead, which both outlives the orchestrator and holds the box awake, making
the task-lease guard redundant. It is sentinel-guarded so a supervisor restart
does not re-run a finished wave, and it stops its own service afterwards so the
sprite can suspend.

logs/WAVE4-DONE records that F3's files were all complete but the worker was
stuck re-running verification it could not finish, so the orchestrator ran the
verification itself and accepted the work. F3's own written report — including
the design critique of the rendered screens it was asked for — was never
produced; that gap is recorded in the sentinel.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014TyzeWmdTqi7U85iYNGy7P

logs/WAVE4-DONE

@@ -0,0 +1,19 @@
+=== WAVE4-DONE written 2026-09-08T21:34Z by the Opus orchestrator ===
+NOT written by service-worker.sh. F3-release's FILES were all complete and
+untouched for ~50 min; it was stuck re-running verification it could not finish
+(600s background-wait ceiling, then a quota wait). The orchestrator ran the
+verification itself, accepted the work, and stopped the service.
+
+Independently verified by the orchestrator (not self-reported):
+  ./tasks/gw assembleDebug     exit 0
+  ./tasks/gw testDebugUnitTest exit 0 -- 102 tests, 1 skipped, 0 failures, 0 errors
+  ./tasks/gw assembleRelease   exit 0
+  app-release.apk 41,777,344 bytes, V2-signed CN=Bookshelf,O=Montanaro (real
+    release key, not the debug cert)
+  keystore + keystore.properties confirmed gitignored, NOT in the commit
+  skipped test = LiveSyncTest (opt-in, needs the live server)
+
+All four F3 tasks DONE: settings-email fix, 5 remaining screens' Paparazzi
+shots (light+dark), release signing + signed APK, top-level README.
+NOT delivered: F3's own written report, incl. its candid design critique of
+the rendered screens. The orchestrator must eyeball the PNGs instead.