#1 Front-side in-flight task tracking: Engine.enter_request now records per-request
   metadata (model/kind/path/started_at) in engine.active; _merge_engine_tasks
   injects synthetic "running" task entries for in-flight requests not already
   reported by the engine (deduped by engine+model). Both the direct proxy and the
   broker route register/clear it. So the Tasks page shows work the front
   dispatched even when the engine is too GIL-busy generating to answer its own
   /admin/api/tasks. (Combines with the last-good cache.)

#3 Thermal stopping-criteria cadence: the per-token callback held the GIL every
   token, starving admin handlers. Now it does real work every 50 tokens for text,
   scaling to every 100 when generation is fast (>50 tok/s) — far less GIL
   contention, negligible thermal-drift risk between checks.

#2 (no change needed): generation already runs OFF the event loop via
   _aiter_blocking (asyncio.to_thread per token step) for streaming and
   asyncio.to_thread(manager.generate) for non-streaming.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>