feat(018): sub-second exits on a dedicated thread + fast decision pipeline

Exits move off the single-threaded scheduler onto their own daemon thread at
1s (mirrors the fast trigger thread). Dedicated research connection (shared
facade isn't thread-safe); scheduler exits step auto-disabled when the thread
runs (single-caller invariant — no racing instance state, no double-submit);
manage() already idempotent (stop ratchets >1c up only). 3 driver tests + 539
suite green. On fast small-caps this is the 'get out fast' the owner asked for.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

deploy/docker/truenas-compose.yml

@@ -78,6 +78,8 @@ x-app: &app
     TRADING_EXIT_TRAIL_AFTER_R: '1.0'
     TRADING_EXIT_TRAIL_MODE: 'prior_low'
     TRADING_EXIT_MANAGE_INTERVAL_SECONDS: '4'  # 12->4s: react to fast small-cap round-trips (was giving back gains)
+    TRADING_EXIT_THREAD_ENABLED: '1'
+    TRADING_EXIT_THREAD_INTERVAL_SECONDS: '1.0'
     TRADING_EXIT_TRAIL_R_STEP: '0.25'
     TRADING_LIQUIDITY_MAX_VOLUME_PCT: '0.025'
     TRADING_MAX_BACKOUTS_PER_SYMBOL: '3'