feat: add a utility to extract selected text with KaTeX support

[pilgrimlyieu]

What this PR does

Before this PR:

• [错误]: quote对于katex会使得其变成多行 #9908
• [功能]: 数学公式/md 内容无法复制或者引用 #6481

After this PR:

Fixes #9908

This PR introduces a utility function getSelectedText to consistently extract selected text for proper handling of KaTeX formulas. The function is integrated across several components to replace direct usage of window.getSelection()?.toString(), ensuring more reliable and feature-rich text selection. Comprehensive unit tests are also added to verify its behavior for plain text, inline and display KaTeX, and mixed content.

Why we need it and why it was done in this way

The following tradeoffs were made:

The following alternatives were considered:

Links to places where the discussion took place:

Breaking changes

If this PR introduces breaking changes, please describe the changes and the impact on users.

Special notes for your reviewer

Checklist

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Approvers are expected to review this list.

• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature.

Release note

NONE

[pilgrimlyieu]

@claude review

[Copilot]

Pull Request Overview

This PR introduces a centralized utility function getSelectedText to handle text selection across the application with special support for KaTeX formulas. The function extracts LaTeX source code from KaTeX elements and wraps them with appropriate delimiters ($ for inline, $$ for display mode), ensuring mathematical formulas are preserved in their original LaTeX format when selected.

Key changes:

• Added getSelectedText utility function in src/renderer/src/utils/selection.ts with KaTeX-aware text extraction
• Comprehensive test suite covering plain text, inline KaTeX, display KaTeX, and mixed content scenarios
• Integrated the utility across components (Chat.tsx, RichEditor/index.tsx, ContextMenu/index.tsx) replacing direct window.getSelection()?.toString() calls

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/renderer/src/utils/selection.ts	New utility function for extracting selected text with KaTeX formula handling
src/renderer/src/utils/tests/selection.test.ts	Comprehensive unit tests for the getSelectedText utility
src/renderer/src/pages/home/Chat.tsx	Integrated getSelectedText for search functionality
src/renderer/src/components/RichEditor/index.tsx	Replaced window.getSelection() calls with getSelectedText utility
src/renderer/src/components/ContextMenu/index.tsx	Updated context menu to use getSelectedText utility

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[MurphyLo]

Note

This comment was translated by Claude.

Hope it can be merged before the next release 🥳

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Original Content

希望能在下次发版前合并🥳