fix(desktop): add native clipboard image paste and fix text paste

[invarrow]

Summary

• Add native clipboard image paste support for the desktop app using Tauri's clipboard-manager plugin
• Fix a bug where text paste was broken because the native clipboard image check ran before checking for text

Problem

Fixes #9868 #12686

When pasting text on the desktop app, the handlePaste function was checking for native clipboard images (via platform.readClipboardImage) before checking if there was text on the clipboard. Since OS clipboards can hold multiple formats simultaneously, this caused stale image data to be returned even when the user copied text, resulting in:

1. Text paste being skipped entirely
2. An old/stale image being pasted instead

Solution

Reordered the paste logic so that:

1. Browser-detected images are handled first
2. Unsupported file types show a toast
3. Plain text is extracted from clipboard
4. Only if there's no text, the native Tauri clipboard is checked for images (e.g., screenshots copied outside the browser)
5. Text is inserted if present

Changes

• packages/app/src/components/prompt-input.tsx: Fixed paste order logic
• packages/app/src/context/platform.tsx: Added readClipboardImage to Platform type
• packages/desktop/src/index.tsx: Implemented readClipboardImage using Tauri plugin
• packages/desktop/package.json: Added @tauri-apps/plugin-clipboard-manager dependency
• packages/desktop/src-tauri/capabilities/default.json: Added clipboard-manager:allow-read-image capability

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Related PRs Found

Based on the search results, here are PRs that appear related to clipboard and paste handling:

1. feat: Pass through data URLs directly and gracefully handle unknown U… #12592 - feat: Pass through data URLs directly and gracefully handle unknown URLs

   • Related to clipboard image handling and data URL processing

2. fix(desktop): windows clipboard images come thru as data not file #12549 - fix(desktop): windows clipboard images come thru as data not file

   • Directly related to desktop clipboard image handling, appears to be a similar issue

3. fix: support reading furl (file URL) from macOS clipboard #6127 - fix: support reading furl (file URL) from macOS clipboard

   • Related to native clipboard image support on macOS

4. fix(tui): support clipboard image paste with proper filename on WSL2 #8209 - fix(tui): support clipboard image paste with proper filename on WSL2

   • Related to clipboard image paste functionality (though for TUI, not desktop)

The most closely related PR is #12549, which also addresses desktop clipboard image issues and may be addressing a related or overlapping problem.

[invarrow]

Fixes #9868 #12686