feat: add live replays and PostgreSQL maintenance tools

- Stream compact live replay updates across local and clustered dashboards.
- Render responsive snake bodies as SVG paths with aligned custom icons.
- Add cache-busted assets, replay fallback routes, and live-follow playback.
- Support PostgreSQL benchmark sampling and idempotent SQLite migration.
- Add dry-run cleanup for old low-quality PostgreSQL replay payloads.
- Reward safe perimeter lanes and bump Prism to version 1.5.0.
- Add backend, migration, dashboard, and perimeter regression coverage.

scripts/cleanup_postgresql_gameplay.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+"""Delete old low-quality replay payloads while preserving game results."""
+
+from __future__ import annotations
+
+import argparse
+import asyncio
+from datetime import datetime, timedelta, timezone
+
+async def cleanup(dsn: str, older_than_days: int, dry_run: bool, vacuum: bool) -> None:
+  try:
+    import asyncpg
+  except ImportError as exc:
+    raise RuntimeError("asyncpg is required for PostgreSQL cleanup") from exc
+
+  cutoff = datetime.now(timezone.utc) - timedelta(days=max(1, older_than_days))
+  connection = await asyncpg.connect(dsn=dsn)
+  try:
+    candidates = int(await connection.fetchval("""
+      SELECT count(*)
+      FROM games
+      WHERE has_replay
+        AND quality_status = 'low_quality'
+        AND COALESCE(ended_at, started_at) < $1
+    """, cutoff))
+    rows = await connection.fetchrow("""
+      SELECT
+        (SELECT count(*) FROM turns t JOIN games g USING (game_id)
+          WHERE g.has_replay AND g.quality_status = 'low_quality'
+            AND COALESCE(g.ended_at, g.started_at) < $1) AS turns,
+        (SELECT count(*) FROM snake_turns t JOIN games g USING (game_id)
+          WHERE g.has_replay AND g.quality_status = 'low_quality'
+            AND COALESCE(g.ended_at, g.started_at) < $1) AS snake_turns,
+        (SELECT count(*) FROM game_snakes t JOIN games g USING (game_id)
+          WHERE g.has_replay AND g.quality_status = 'low_quality'
+            AND COALESCE(g.ended_at, g.started_at) < $1) AS game_snakes
+    """, cutoff)
+    print(
+      f"candidates before {cutoff.isoformat()}: games={candidates:,}, "
+      f"turns={rows['turns']:,}, snake_turns={rows['snake_turns']:,}, "
+      f"game_snakes={rows['game_snakes']:,}"
+    )
+    if dry_run or candidates == 0:
+      print("dry run: no rows changed" if dry_run else "nothing to clean")
+      return
+
+    async with connection.transaction():
+      game_ids = await connection.fetch("""
+        SELECT game_id FROM games
+        WHERE has_replay
+          AND quality_status = 'low_quality'
+          AND COALESCE(ended_at, started_at) < $1
+        FOR UPDATE
+      """, cutoff)
+      ids = [row["game_id"] for row in game_ids]
+      await connection.execute("DELETE FROM snake_turns WHERE game_id = ANY($1::text[])", ids)
+      await connection.execute("DELETE FROM turns WHERE game_id = ANY($1::text[])", ids)
+      await connection.execute("DELETE FROM game_snakes WHERE game_id = ANY($1::text[])", ids)
+      await connection.execute("""
+        UPDATE games
+        SET has_replay = FALSE, quality_status = 'low_quality'
+        WHERE game_id = ANY($1::text[])
+      """, ids)
+    print(f"cleaned replay payloads for {len(ids):,} games; result rows preserved")
+    if vacuum:
+      await connection.execute("VACUUM (ANALYZE) games")
+      await connection.execute("VACUUM (ANALYZE) game_snakes")
+      await connection.execute("VACUUM (ANALYZE) turns")
+      await connection.execute("VACUUM (ANALYZE) snake_turns")
+      print("vacuum/analyze complete")
+  finally:
+    await connection.close()
+
+def main() -> None:
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument("--dsn", required=True)
+  parser.add_argument("--older-than-days", type=int, default=30)
+  parser.add_argument("--execute", action="store_true", help="Apply deletion; default is dry-run")
+  parser.add_argument("--vacuum", action="store_true")
+  args = parser.parse_args()
+  asyncio.run(cleanup(args.dsn, args.older_than_days, not args.execute, args.vacuum))
+
+if __name__ == "__main__":
+  main()