Added per-line copy button for AI response

[mrfandu1]

---

name: Feature Added
about: Added Copy Buttons for per-line Text and Codeblock

Summary of Changes

This PR implements line-by-line copy functionality for AI responses in the AskView component, addressing the need to copy individual lines instead of entire response blocks.

Key Features Added:

• Dynamic Copy Button: Appears next to text lines on hover for precise line copying
• Smart Positioning: Automatically adjusts position for list items, nested content, and regular text
• Persistent Visibility: Button remains visible at last position after mouse leaves text
• Visual Feedback: Highlights hovered line and shows copy confirmation with icon animation
• Performance Optimized: Uses Map-based timeout management and element caching

Related Issue

• Closes #102

This change addresses the workflow friction described in issue #102 where users needed to copy specific lines from AI responses but were forced to copy entire blocks, making line-by-line iteration for debugging, shell commands, or documentation unnecessarily difficult.

Contributor's Self-Review Checklist

Please check the boxes that apply. This is a reminder of what we look for in a good pull request.

• [✔] I have read the CONTRIBUTING.md document.
• [✔] My code follows the project's coding style and architectural patterns as described in DESIGN_PATTERNS.md.
• [✔] I have added or updated relevant tests for my changes.
• [✔] I have updated the documentation to reflect my changes (if applicable).
• [✔] My changes have been tested locally and are working as expected.

Additional Context (Optional)

Technical Implementation Details:

New Features:

1. Dynamic Copy Button System:

   • Automatically positions copy buttons next to text elements on hover
   • Handles different content types (paragraphs, headings, list items, blockquotes)
   • Smart positioning logic prevents conflicts with bullet points and nested content

2. Optimized Performance:

   • Map-based timeout management for better memory handling
   • Element caching to reduce DOM queries
   • Passive event listeners for improved scroll performance

3. Enhanced UX:

   • Button persists at last position (no more chasing disappearing buttons)
   • Visual feedback with text highlighting and icon animations
   • Proper pointer cursor behavior

Code Architecture:

• Follows existing LitElement patterns
• Uses CSS custom properties for consistent styling
• Implements proper cleanup in disconnectedCallback()
• Maintains backward compatibility with existing copy functionality

Testing Notes:

• Tested with various content types (code blocks, lists, paragraphs)
• Verified positioning accuracy across different text structures
• Confirmed proper cleanup and memory management
• Validated accessibility with keyboard navigation

pr2.mp4

pr1.mp4

[mrfandu1]

@samtiz @jhyang0 Please review this PR, and lemme know if any other changes required

[tarsyang]

Nice! I'll review it