Address fifth Copilot review: thread safety, MQTT precision, integer timestamps

override_manager.py:
- get_override() now returns a defensive copy via dataclasses.replace()
  instead of the live internal OverrideState instance; callers (including
  other threads) can no longer mutate expires_at/charge_rate without
  holding the manager lock, preserving the thread-safety guarantee

mqtt_api.py:
- publish_override_duration() changed from :.0f to :.1f so that
  fractional-minute durations (e.g. 45.5) are published accurately
  instead of being silently rounded to the nearest whole minute

mcp_server.py:
- _format_forecast_array() now uses integer floor division for base_time
  (int(run_time) // interval_seconds * interval_seconds) and casts each
  time_start to int, eliminating floating-point drift in JSON timestamps

All 373 tests pass; pylint 9.46/10.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: MaStr

src/batcontrol/mcp_server.py

@@ -60,12 +60,12 @@ def _format_forecast_array(arr, run_time: float, interval_minutes: int,
     if arr is None:
         return []
     interval_seconds = interval_minutes * 60
-    base_time = run_time - (run_time % interval_seconds)
+    base_time = (int(run_time) // interval_seconds) * interval_seconds
     result = []
     for i, val in enumerate(arr):
         result.append({
             'slot': i,
-            'time_start': base_time + i * interval_seconds,
+            'time_start': int(base_time + i * interval_seconds),
             'value': round(float(val), digits),
         })
     return result

src/batcontrol/mqtt_api.py

@@ -464,7 +464,7 @@ def publish_override_duration(self, duration_minutes: float) -> None:
         if self.client.is_connected():
             self.client.publish(
                 self.base_topic + '/override_duration',
-                f'{duration_minutes:.0f}')
+                f'{duration_minutes:.1f}')
 
     def publish_production_offset(self, production_offset: float) -> None:
         """ Publish the production offset percentage to MQTT

src/batcontrol/override_manager.py

@@ -9,7 +9,7 @@
 import time
 import threading
 import logging
-from dataclasses import dataclass, field
+from dataclasses import dataclass, field, replace
 from typing import Optional
 
 logger = logging.getLogger(__name__)
@@ -117,8 +117,9 @@ def clear_override(self) -> None:
             self._override = None
 
     def get_override(self) -> Optional[OverrideState]:
-        """Get the active override, or None if no override is active.
+        """Get a snapshot of the active override, or None if no override is active.
 
+        Returns a defensive copy so callers cannot mutate the internal state.
         Automatically clears expired overrides.
         """
         with self._lock:
@@ -131,7 +132,7 @@ def get_override(self) -> Optional[OverrideState]:
                 )
                 self._override = None
                 return None
-            return self._override
+            return replace(self._override)
 
     def is_active(self) -> bool:
         """Check if an override is currently active (not expired)."""