Design document for Tier 1 UX enhancement implementing toast
notifications using sonner library.
- Comprehensive context on current state problems
- Phase-by-phase implementation plan
- Design patterns and best practices
- Complete verification checklist
- Risk assessment and mitigation strategies
Related: #33, #34, #35
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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