[mbreiser]

Stacked on #261 (claude/scanimage-frames-wrapper), so this diff is only the SiPM commit. Retarget to main once #261 merges.

Implements LAB-319 (split out of LAB-308, ScanImage documentation for agents, Bergamo III); uses the LAB-303 connector pattern.

Why

The SiPM detector settings (bias, enable, offsets, bandwidth, temperature) are not in ScanImage or its TIFF header. This node reads them through the vendor ThorSiPM.dll and publishes them as a connector, so they land in the run log and bag next to ScanImage and the arena.

What

• ros2-poc/nodes/thorsipm.py — ctypes driver, no ROS. Binds only FindDevices, SelectDevice, GetParam, GetParamString, GetParamInfo, TeardownDevice (signatures from the vendor GUI's own P/Invoke metadata). No write path. CLI: scan / snapshot / watch. FakeBackend simulates the controller.
• ros2-poc/nodes/sipm_node.py, sipm_cmd.py — /sipm/cmd, /sipm/reply, /sipm/status (1 Hz), std_msgs/String JSON like the BIAS and ScanImage connectors. Commands: ping, status, get, info, scan, disconnect, reconnect. Keeps reporting (and retrying) while the vendor GUI holds the COM port.
• bridge_node.py, mcap_convert.py, rig.py --sipm, pixi tasks (sipm-node, sipm-cmd, sipm, test-sipm) — the sipm connector is recorded and derived like the others.

Open question the rig test answers

The GUI's Params enum gives the IDs for enable, gain, offset, bandwidth, safety, saturations and serial numbers. The DLL also names PARAM_SIPM1_BIAS, …_TEMPERATURE, …_TEMPSTATUS, but their numeric IDs aren't in the enum. Block S finds them with a read-only GetParamInfo scan and writes them to config/sipm_params.json in scanimage-2026-bergamo.

Testing

• pixi run test-sipm: 28 / 28 (driver, node, busy port, recording) on macOS.
• Existing suites unchanged: test-frames 39 / 39, test 54 / 54.
• Dry run of the rig command with --fake: 16 "src":"sipm" connector events in the run log, bag closed cleanly, controller released on exit.
• Not yet run on the real controller or on Windows. Rig procedure: rig-session-sipm-block-s.md.

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