chore(db): raise ticket WIP limit 3 → 5

Per maintainer call — 3 was too tight for the parallel Phase 4 work in
flight; 5 better matches how many tickets are genuinely active at once.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tooling/db/ticket

@@ -38,7 +38,7 @@ sys.path.insert(0, str(Path(__file__).resolve().parent))
 
 from common import get_connection, load_config  # noqa: E402
 
-WIP_LIMIT = 3
+WIP_LIMIT = 5
 
 
 def query(conn, sql, params=()):