telemetry: add cruise engagement state for desync debugging

Added brakePressed to cruise group, prev_cruise_button and
prev_main_button to buttons group in carstate telemetry. New "engage"
group in controlsd logs state machine state, enabled/active flags, and
stock cruise state every frame for tracing engagement desync bugs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/controls/controlsd.py

@@ -37,6 +37,7 @@ from openpilot.system.version import get_short_branch
 from openpilot.selfdrive.frogpilot.controls.lib.frogpilot_functions import CRUISING_SPEED, PROBABILITY, MovingAverageCalculator
 
 from openpilot.selfdrive.frogpilot.controls.lib.model_manager import RADARLESS_MODELS
+from openpilot.selfdrive.clearpilot.telemetry import tlog
 from openpilot.selfdrive.frogpilot.controls.lib.speed_limit_controller import SpeedLimitController
 
 SOFT_DISABLE_TIME = 3  # seconds
@@ -628,6 +629,16 @@ class Controls:
     # Check if openpilot is engaged and actuators are enabled
     self.enabled = self.state in ENABLED_STATES
     self.active = self.state in ACTIVE_STATES
+
+    # CLEARPILOT: log engagement state for debugging cruise desync issues
+    tlog("engage", {
+      "state": self.state.name,
+      "enabled": self.enabled,
+      "active": self.active,
+      "cruise_enabled": CS.cruiseState.enabled,
+      "cruise_available": CS.cruiseState.available,
+      "brakePressed": CS.brakePressed,
+    })
     if self.active:
       self.current_alert_types.append(ET.WARNING)