pl2303 built out of tree for the IMU's PL2303GC adapter; BOM and rebuild procedure

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

docs/BOM.md

@@ -181,8 +181,10 @@ Header facts (carrier board spec SP-11324-001 v1.3, Table 3-3 and 5-3; raw copy
 - Do not zero the accelerometer at startup the way smart-serow's `imu_calibrate()` does: that removes gravity, which tilt and grade need.
 - The serial device belongs to `dialout` (the header's `/dev/ttyTHS1` and USB adapters alike); a service gets it with
   `SupplementaryGroups=dialout`, not by adding users to the group.
-- **USB-UART adapter:** JetPack's kernel has drivers for CP210x and FTDI only (no PL2303, no CH341). In use: a CP2102 (`10c4:ea60`,
-  generic serial `0001`, so it can only be told apart by port). A PL2303GC (`067b:23a3`) enumerates but gets no driver.
+- **USB-UART adapter: a PL2303GC (`067b:23a3`)**, the one the IMU enclosure is designed around (2026-10-14). JetPack's kernel has
+  drivers for CP210x and FTDI only, so `pl2303` is built out of tree in `~/infra/pl2303/` ([report](impl/reports/PL2303-DRIVER.md));
+  rebuild it after a kernel update. A CP2102 (`10c4:ea60`, generic serial `0001`) was used for the first test and works with no
+  build. Neither has a unique serial: the `imu` service finds the WT61 by trying each adapter, so they are interchangeable.
 - The temperature field is the chip's own temperature, not the air's: `raw / 340 + 36.53` °C per the datasheet (smart-serow's `IMU.md`
   says 36.25).
 - **The gyro zeroes itself at power-up**, and yaw resets to 0. The module must be still while it powers up; it is, if it powers with the