Summary

• default primary-selection middle-click paste on for macOS as well as Linux
• keep Windows opt-in because the single Orca toggle also enables copy-on-select capture
• add a migration guard for the widened platform default while preserving previous Linux and macOS opt-outs

Validation

• pnpm exec vitest run --config config/vitest.config.ts src/shared/constants.test.ts src/main/persistence.test.ts src/main/ghostty/mapper.test.ts
• pnpm run typecheck:node
• pnpm run typecheck:web
• pnpm run typecheck:cli
• pnpm run lint