feat(oneshot): add ONESHOT_DEBUG verbose logging mode

Adds a debug flag (ONESHOT_DEBUG=true / --debug / npm run oneshot-debug)
that surfaces the engine's internal decision process at every key step.

Debug output tags
─────────────────
  [DBG:FEED]   — Market discovery: every slug probed, API response status,
                 token IDs extracted, tick size fetched.
                 Throttled poll summary every 10 ticks per market showing
                 bid/ask/spread/mid/depth for both UP and DOWN sides.

  [DBG:GATE]   — Hard gate result every 5 evaluations per market:
                 TTE range, spread width, depth thinness, stale flag.
                 Shows exact gate fail reason or PASS confirmation.

  [DBG:FEAT]   — Feature breakdown for each side every 5 evals:
                 slope, imbalance, spread, retrace raw values plus
                 per-component scores and weighted total.

  [DBG:SCORE]  — Per-side qualify check: score vs threshold,
                 trend confirm flag, and QUALIFY / skip verdict.

  [DBG:SIGNAL] — Always logged (no throttle) when an ENTER signal fires.

  [DBG:HEART]  — 5-second heartbeat: active markets, per-market SM state,
                 dailyPnl, consecLosses, cooldownLeft, halted flag.

New script
──────────
  npm run oneshot-debug  →  DRY_RUN=true ONESHOT_DEBUG=true node src/oneshot.js

Co-Authored-By: direkturcrypto <direkturcrypto.x@mail3.me>

.env.example

@@ -166,3 +166,8 @@ ONESHOT_DAILY_LOSS_CAP=20
 
 # Maximum milliseconds to wait for a FOK fill ack (timeout → cancel → IDLE)
 ONESHOT_FILL_TIMEOUT_MS=800
+
+# Enable verbose debug logging (discovery probes, gate results, feature scores, heartbeat)
+# Can also be enabled with: npm run oneshot-debug
+# Or on the command line: ONESHOT_DEBUG=true npm run oneshot
+ONESHOT_DEBUG=false