v1.2.1

Fix macOS "damaged app" by ad-hoc signing the build (1.2.1)

The unsigned macOS builds shipped with no _CodeSignature/CodeResources
because electron-builder skips signing entirely under
CSC_IDENTITY_AUTO_DISCOVERY=false. Once a download picked up the
quarantine flag, macOS reported "TreeMap is damaged and can't be opened"
and refused to launch it — a dead end with no right-click-to-open escape.

Add an afterPack hook that ad-hoc signs the bundle inside-out, producing a
valid signature so a download shows the dismissable "unidentified
developer" prompt instead. README documents the one-time
`xattr -dr com.apple.quarantine` fallback for already-broken downloads.

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