Fix control panel freeze and CM1 motor not moving

ControlWidget._write() called dev.write_channel() directly on the GUI
thread from Qt signal handlers — for CML (CoolMuscle), write() does 2-3
blocking serial round-trips, and a slider fires valueChanged on every drag
tick, so each tick froze the whole app until the device responded or timed
out. Replaced with a coalescing background dispatch: writes are keyed by
(device, channel) in a dict instead of a plain FIFO queue, so re-writing
the same channel while a write is still pending updates its value in place
rather than piling up — a strict FIFO was observed backing up 30+ deep
during a single drag, meaning the motor kept "moving" to seconds-old
positions long after the slider stopped, which looked like a freeze even
once off the GUI thread.

Separately, the motor never actually moved because it was never enabled:
per docs/CM1-C_ASCII_Command_Cheatsheet.md, a CM1-C motor stays disabled
("shaft free") until sent "(", and nothing in CMLLayer.write()'s VS/MA
handling ever sent it — enable only existed as a separate M1_ME channel
the generic MotorControl widget has no concept of. VS/MA now send enable
unconditionally before the move sequence (a no-op if already enabled).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/api_layers/protocols/cml.py b/api_layers/protocols/cml.py
index 113afe7..e085adf 100644
--- a/api_layers/protocols/cml.py
+++ b/api_layers/protocols/cml.py
@@ -149,6 +149,16 @@ class CMLLayer(BaseProtocol):
                     self._send(motor.address, "]")
                     self._read_reply()
                 elif cmd == "VS":
+                    # Motor must be enabled ("(") or the shaft stays free and
+                    # every move command below is silently accepted but
+                    # produces no motion — see docs/CM1-C_ASCII_Command_
+                    # Cheatsheet.md "Safety and enable commands". Enabling
+                    # an already-enabled motor is a no-op, so it's safe to
+                    # send unconditionally on every move rather than relying
+                    # on the operator to have pressed a separate M1_ME
+                    # control first.
+                    self._send(motor.address, "(")
+                    self._read_reply()
                     self._send(motor.address, "P0", _CONTINUOUS_POSITION)
                     self._read_reply()
                     self._send(motor.address, "S0", int(value))
@@ -156,6 +166,8 @@ class CMLLayer(BaseProtocol):
                     self._send(motor.address, "^")
                     self._read_reply()
                 elif cmd == "MA":
+                    self._send(motor.address, "(")
+                    self._read_reply()
                     self._send(motor.address, "P0", int(value))
                     self._read_reply()
                     self._send(motor.address, "^")