Remove files that should never have been tracked:
- pi-mono-reference/: 688-file copy of an upstream monorepo, zero imports,
used only as offline human reference
- build/electron-builder.runtime.json: environment-specific build artifact
with hardcoded local paths
- state/cancel-signal-state.json: runtime state written by the app
- prompt.txt, logo.svg (root): exact duplicates of the canonical copies
under .planning/archive/ and assets/
Add state/ to .gitignore so future runtime state stays out.