Hardening round 2: healthcheck, audit anchor, return_4h, exec config, signals

Sei interventi MEDIA priorità sul sistema. 323 test pass, mypy strict
pulito, ruff clean.

1. Docker HEALTHCHECK + cerbero-bite healthcheck:
   - nuovo subcommand che esce 0 se kill_switch=0 e last_health_check
     entro --max-staleness-s (default 600s);
   - HEALTHCHECK direttiva nel Dockerfile (60s interval, 5s timeout,
     start_period 120s, retries 3);
   - healthcheck definition nel docker-compose.yml.

2. Audit hash chain anti-truncation:
   - migration 0002: nuova colonna system_state.last_audit_hash;
   - AuditLog accetta callback on_append, dependencies.py la wire al
     repository.set_last_audit_hash;
   - Orchestrator.boot verifica che il tail file matcha l'anchor
     persistito; mismatch → kill switch CRITICAL.

3. return_4h bootstrap da deribit get_historical:
   - quando dvol_history è vuoto _fetch_return_4h cade su
     deribit.historical_close (1h candle 4h fa);
   - alert LOW se anche il fallback fallisce.

4. execution.environment + execution.eur_to_usd in strategy.yaml:
   - ExecutionConfig promosso a typed schema con i due campi
     consumati al boot;
   - CLI start preferisce i valori da config; CLI flag overridano
     solo quando differenti dai default.

5. Cycle correlation ID:
   - structlog.contextvars.bind_contextvars in run_entry/run_monitor/
     run_health propaga cycle_id e cycle nei log strutturati.

6. SIGTERM/SIGINT clean shutdown:
   - run_forever installa loop.add_signal_handler per SIGTERM e
     SIGINT; il segnale set()ta un asyncio.Event che termina il
     blocco principale, scheduler.shutdown e ctx.aclose finalizzano.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/cerbero_bite/runtime/monitor_cycle.py

@@ -154,13 +154,19 @@ def _option_type_from_name(name: str) -> PutOrCall:
 
 
 async def _fetch_return_4h(ctx: RuntimeContext, *, now: datetime) -> Decimal:
-    """Compute ETH 4h return from the locally stored dvol_history snapshots.
+    """Compute ETH 4h return.
 
-    The orchestrator records a snapshot at the start of every monitor
-    cycle (see :func:`run_monitor_cycle`); this helper reads the most
-    recent snapshot at least 3.5h old and computes ``(now / past) - 1``.
-    Returns 0 if no historical sample is available — in that branch the
-    orchestrator emits a LOW alert about insufficient history.
+    Resolution order:
+
+    1. local ``dvol_history`` snapshot at least 3h30 old (recorded by
+       previous monitor cycles);
+    2. Deribit ``get_historical`` 1h candles 4h ago — bootstrap when
+       SQLite has no recent sample (first cycle after a fresh
+       container, or after long downtime).
+
+    Returns ``0`` only when both sources fail; in that case the
+    monitor cycle emits a LOW alert and exit_decision falls back to
+    HOLD on the adverse-move trigger.
     """
     cutoff = now - timedelta(hours=3, minutes=30)
     floor = now - timedelta(hours=8)
@@ -174,13 +180,30 @@ async def _fetch_return_4h(ctx: RuntimeContext, *, now: datetime) -> Decimal:
         ).fetchone()
     finally:
         conn.close()
-    if row is None:
-        return Decimal("0")
-    past_spot = Decimal(str(row[1]))
-    if past_spot == 0:
+    if row is not None:
+        past_spot = Decimal(str(row[1]))
+        if past_spot != 0:
+            spot_now = await ctx.deribit.index_price_eth()
+            return spot_now / past_spot - Decimal("1")
+
+    # Fallback: ask Deribit for the 4h candle close.
+    try:
+        past_close = await ctx.deribit.historical_close(
+            instrument="ETH-PERPETUAL",
+            start=now - timedelta(hours=5),
+            end=now - timedelta(hours=3, minutes=30),
+            resolution="1h",
+        )
+    except Exception:  # pragma: no cover — defensive, surface as LOW alert
+        past_close = None
+    if past_close is None or past_close == 0:
+        await ctx.alert_manager.low(
+            source="monitor_cycle",
+            message="no return_4h sample available (history empty + bootstrap failed)",
+        )
         return Decimal("0")
     spot_now = await ctx.deribit.index_price_eth()
-    return spot_now / past_spot - Decimal("1")
+    return spot_now / past_close - Decimal("1")
 
 
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