P0-07: Untrack TreeHouse_Controllers/.vscode cache and add PlatformIO ignores #185

Part of #175 (audit Phase 0). Evidence: docs/audit/2026-11-09/detail/firmware-prototypes-pipes.md §1e, §5.

Why. Firmware/TreeHouse_Controllers/.vscode/c_cpp_properties.json (538 lines, 68 KB; 483 lines contain another machine's home directory) and .vscode/launch.json (44 lines, absolute paths, header says "AUTOMATICALLY GENERATED FILE") are tracked despite being listed in that project's own .gitignore:3-5. git ls-files -i -c --exclude-standard confirms. The root .gitignore has no PlatformIO patterns, so the next PlatformIO project can repeat this. Also stale in root .gitignore: line 17 layout_calibrated.json (file removed by ADR-0015) and the line 18 comment about touch_test_pygame.py (no longer exists).

Do.

git rm --cached Firmware/TreeHouse_Controllers/.vscode/c_cpp_properties.json Firmware/TreeHouse_Controllers/.vscode/launch.json

Add to root .gitignore:

**/.pio/
**/.vscode/c_cpp_properties.json
**/.vscode/launch.json
**/.vscode/ipch/

Delete .gitignore:17 and fix the comment at :18.

Done when. git ls-files -i -c --exclude-standard prints nothing.