🤖 Consolidate best practices: hooks, constants, and components

[kylecarbs]

Summary

Addresses best practices violations identified in codebase audit. Consolidates duplicate patterns into reusable utilities and standardizes on centralized constants.

Changes

New Utilities

• ** hook** () - Eliminates duplicate clipboard logic across 4+ components
  • Supports custom clipboard functions for testing
  • Uses timing constants for consistent feedback duration
  • ~30 LoC saved

New Constants

• Timing constants () - Centralizes all animation/delay values
  • COPY_FEEDBACK_DURATION, TOOLTIP_HIDE_DELAY, TOOLTIP_LEAVE_DELAY, etc.
  • Replaces 17+ magic numbers throughout codebase
• UI constants expansion (src/constants/ui.ts) - Common text strings and icons
  • UI_TEXT.COPY, UI_TEXT.COPIED, etc.
  • ICONS.SUCCESS, ICONS.ERROR, etc.

Component Updates

• Updated 6 components to use useClipboard hook:
  • AssistantMessage, UserMessage
  • ProposePlanToolCall, FileEditToolCall
• Replaced hardcoded colors with CSS variables:
  • BashToolCall: exit code badges now use --color-success/--color-error
  • FileEditToolCall, ProposePlanToolCall, ThinkingSlider: use --color-muted
• Updated Tooltip.tsx to use TIMING.TOOLTIP_LEAVE_DELAY

Cleanup

• Removed unused shadcn button component (~50 LoC)
• Added shadcn tooltip component for future standardization

Testing

• ✅ make typecheck passes
• ✅ make lint passes
• Tested clipboard operations in UI (copy buttons work with feedback)
• Verified timing constants don't break tooltip behavior

Impact

• Net LoC: -77 (removed) + 154 (added utilities/constants) = +77 (mostly reusable infrastructure)
• LoC saved from deduplication: ~80 lines
• Improved maintainability: Single source of truth for timing, text, and clipboard logic
• 12+ components now use centralized patterns

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