Write a bring-up plan

The plan should catch an assembly fault before it destroys anything, and point to the faulty part when a reading is wrong. Compute every expected number from the schematic and datasheets, and show the working so the number can be recomputed after a change. Read the circuit (kicad-view: the sheet plots and the pin list) and the design notes first.

TEST_PLAN.md layout

1. Header: the board, its revision, and the schematic the numbers come from. Run the stages in order and stop at the first failure.
2. Circuit summary: the blocks, their parts, and where to probe each.
3. Stages 0–3: one table per stage, with the columns # | Measure / do | Expect | A wrong reading means.
4. Log: one copy per board serial: date, tester, each reading, pass or fail.

Stage 0: visual, unpowered

Name the fine-pitch parts and the pin pairs most likely to bridge, the polarised parts, and the parts easy to swap (same package, different value).