v1.12.1: stop-handler writes terminal status + constraint cleanup + dead code removal

- handleAbortOrError now writes status='cancelled' on user stop; rows
  no longer stuck 'streaming' forever
- Drop stale messages_status_check constraint (only messages_status_chk
  remains, allowing 'cancelled' via TS MESSAGE_STATUSES)
- Remove detectSameNameLoop and DOOM_LOOP_SAME_NAME_THRESHOLD (added
  during 2026-05-21 debugging spike, never fired in any real run,
  existing detectDoomLoop covers actual failure modes)
- Remove 12 ctx.log.info diagnostic markers added during the same
  spike (verbose for production)
- Bundles workspace pane sync + status indicator overhaul +
  startup hung-row sweep landed earlier in v1.12.1 work

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/schema.sql

@@ -120,6 +120,19 @@ BEGIN
   END IF;
 END $$;
 
+-- v1.12.1: drop stale inline CHECK constraints that were superseded by the
+-- named *_chk variants above. messages_status_check missed 'cancelled' and
+-- messages_role_check missed 'system' — both narrower than what's in use.
+DO $$
+BEGIN
+  IF EXISTS (SELECT 1 FROM pg_constraint WHERE conname = 'messages_status_check') THEN
+    ALTER TABLE messages DROP CONSTRAINT messages_status_check;
+  END IF;
+  IF EXISTS (SELECT 1 FROM pg_constraint WHERE conname = 'messages_role_check') THEN
+    ALTER TABLE messages DROP CONSTRAINT messages_role_check;
+  END IF;
+END $$;
+
 -- v1.2-project-ux: projects.status + projects.gitea_remote
 -- KEEP IN SYNC: apps/server/src/types/api.ts PROJECT_STATUSES
 ALTER TABLE projects ADD COLUMN IF NOT EXISTS status TEXT NOT NULL DEFAULT 'open';