Clean up hardware repo: kill the resurrecting stale power sheet, restore datasheets

- Remove stale lowercase power.kicad_sch (pre-rework draft; live sheet is
  Power.kicad_sch). Both paths were git-tracked, which on a case-insensitive
  Windows checkout makes them one file on disk - deleting the stale one also
  deleted the live one, and restoring the live sheet resurrected the stale
  path at the next commit. Removing the path from the index breaks the loop.
- Remove re-bba-rb.kicad_pcb.old.* leftovers (recoverable from history).
- Restore hardware/re-bba-rb/datasheets/ (deleted accidentally by 3547302)
  and add the two missing datasheets: TPS22810 (power) and PUSB3AB6 (exi).
- Add hardware/re-bba-rb/TODO.md capturing the 2026-07-17 review findings
  (EXI DO/DI swap, missing W5100S MDI termination, FTDI EEPROM resistors,
  iceprog pin mismatch, PR1 margin, BOM/ordering notes); referenced from
  CLAUDE.md.

Verified after cleanup: ERC 0 violations, netlist identical (107 components).

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

CLAUDE.md

@@ -253,6 +253,15 @@ reference implementations — use `amaranth.lib.cdc` primitives (`FFSynchronizer
 plug (schematic, PCB, custom GameCube symbol library). Used to verify pad geometry
 before ordering the interposer PCB; not part of the FPGA build.
 
+`hardware/re-bba-rb/` — the actual adapter PCB (FT2232H + iCE40UP5K + W5100S,
+powered from SP1 12 V via buck). **Open findings from the 2026-07-17 hardware
+review live in `hardware/re-bba-rb/TODO.md`** — read it before editing the
+schematics, ordering boards, or writing the board PCF. Highlights: EXI DO/DI are
+swapped vs the (incorrect) SP1 table in `docs/gc_bba_fpga_design.md` (DO = GC→
+adapter = MOSI); the W5100S MDI 49.9 Ω termination network is missing; the FTDI
+EEPROM needs its 2.2 k/10 k resistors; stock iceprog doesn't match the FTDI pin
+mapping.
+
 ---
 
 ## Amaranth Simulator API