feat: add spindle direction selection contract

docs/LLM_CONTEXT.md

@@ -141,7 +141,7 @@ Program execution exists as a contract scaffold and future path, but the v1 prod
 ### v1 must include
 
 - `MANUAL` state reachable from `IDLE` only.
-- Operator live controls for force, table RPM, spindle RPM, and optional force modulation.
+- Operator live controls for force, table RPM, spindle RPM, spindle rotation direction (`cw`/`ccw`), and optional force modulation.
 - Mandatory geometric gate before `MANUAL` or `RUNNING`.
 - Full telemetry at **≥100 Hz** with a single Teensy monotonic timestamp source.
 - Manual-session log emitted on exit.
@@ -214,7 +214,7 @@ Shop-floor sequence:
    - `configured_arm_amplitude_deg`
    - `configured_arm_center_deg`
 5. Operator confirms each value; no skip path.
-6. Operator enters initial force, table RPM, spindle RPM, optional modulation.
+6. Operator enters initial force, table RPM, spindle RPM, spindle rotation direction (`cw`/`ccw`), optional modulation.
 7. Host sends `MANUAL_START`; Teensy ACK/NACKs.
 8. Telemetry begins at ≥100 Hz.
 9. Operator adjusts live setpoints; each change is logged as an event.
@@ -263,6 +263,8 @@ Shop-floor sequence:
 - `force_setpoint_n`
 - `table_rpm_setpoint`
 - `spindle_rpm_setpoint`
+- `spindle_direction_setpoint`
+- `spindle_direction_actual`
 - `force_actuator_cmd`
 - `estop_active`
 - `interlock_state`