Render inline notes with side-aware range guides

[benvinegar]

Summary

• replace the floating note overlay with inline note cards that sit in the diff flow
• add side-aware split-view note presentation so notes dock to the old/new side and use an outer guide lane instead of replacing diff rails
• add a dedicated violet note palette plus updated UI coverage for the inline card, range guide, and bootstrap note state

Testing

• bun test test/ui-components.test.tsx test/app-interactions.test.tsx
• bun run typecheck
• bun run test:tty-smoke