Acquire and hold RESERVE_BEHAVIORS behavior control

[infraax]

Task: Behavior Control Acquisition

Parent epic: #4 (M1 — Robot Connection)
Depends on: #16 (ConnectionManager)

What to do

After a successful SDK connection, acquire RESERVE_BEHAVIORS at Priority 30 and hold it for the session. This gives VectorBrain SDK control while allowing safety behaviors to preempt us.

// In ConnectionManager.Start(), after dial succeeds:
stream, err := client.BehaviorControl(ctx)
// Send ControlRequest with RESERVE_BEHAVIORS at Priority 30
// Keep the stream alive — releasing it surrenders control
// Re-acquire on reconnect

Why RESERVE not OVERRIDE

Safety behaviors (cliff detection, fall response) run at Priority 10 — lower number = higher priority. RESERVE (Priority 30) means we can be preempted. OVERRIDE would suppress safety behaviors. We never use OVERRIDE.

This is documented in CLAUDE.md as a non-negotiable constraint.

Reconnect behavior

If the connection drops and reconnects, re-acquire behavior control immediately after re-dial.

Notes

• The control stream must be held alive for the duration of the session. If the stream closes, control is lost.
• Log acquisition and loss of control at INFO level — this is important operational state.
• HasControl bool should be exposed on ConnectionManager and reflected in RobotState.

Definition of done

RobotState.has_sdk_control is true when connected. Verified that cliff detection still stops Vector (safety not overridden).