release: Floatick 0.3.0

[lucaslus]

Summary

• Adds one-click Markdown copy for complete todo handoff to AI agents.
• Consolidates todo actions into a consistent bottom-sheet interaction while keeping tags directly accessible.
• Adds configurable collapse-on-outside-click behavior and improves floating-window restore, placement, and Dock attention feedback.
• Optimizes large-list scrolling with indexed derived state, lazy rows, viewport prefetch, and benchmark coverage.

Release candidate

• Version: 0.3.0+7
• Accepted candidate: e021b3cdfdbe833ba8b411137c84ba5211d47509
• Draft build: https://github.com/lucaslushuo/floatick/actions/runs/30442601697
• Universal DMG SHA-256: 5ff8ab9092b7ac4ba8436bc5e7b07288b032cf3a6eaded493608f3345df8f0d0

Validation

• Flutter formatting and static analysis
• 123 Flutter tests
• Three real-engine macOS UI automation journeys
• Six native AppKit boundary tests
• 10,000-todo data and scroll benchmarks
• Universal arm64 and x86_64 release build plus isolated launch smoke test

This PR must be merged with a merge commit so the accepted candidate remains reachable from main. No release artifact will be rebuilt during promotion.