[Feature] Add setting to auto-expand diffs in "Roo wants to edit this file" chat messages

[jcalfee]

Before expansion:

After clicking on the file name, expansion:

Feature Request

Problem Description:
The diff in "Roo wants to edit this file" messages uses a collapsible <details> element with the filename as <summary>, requiring a click on the gray bar to expand. This interrupts workflow for quick reviews, especially since diffs calculate upfront but aren't auto-visible.

Proposed Solution:
Add a boolean setting roo.fastEdits.autoExpandEditDiffs (default: false) in package.json under contributes.configuration.properties. This exposes it in VS Code/VSCodium Settings (searchable under "Roo Fast Edits") and optionally in any custom settings UI (e.g., via settingsPanel.ts).

In the edit message formatter (e.g., editProposalService.ts or chatHandler.ts), check the setting and append open to <details> if true: <details open><summary>[filename] +X -Y</summary><pre><code class="language-diff">[diff]</code></pre></details>.

This auto-expands cleanly, preserves syntax highlighting, and avoids JS/CSS hacks. Test for large diffs/perf. References bug #10855.

[roomote]

I've analyzed this issue and here's my proposed implementation plan:

Summary

Add a setting to auto-expand diffs in "Roo wants to edit this file" chat messages.

Implementation Plan

1. Add VSCode Setting in src/package.json

Add a new boolean setting roo-cline.autoExpandEditDiffs (default: false) under contributes.configuration.properties:

"roo-cline.autoExpandEditDiffs": {
  "type": "boolean",
  "default": false,
  "description": "Automatically expand diffs when Roo wants to edit files"
}

2. Add Type Definition in packages/types

Add autoExpandEditDiffs?: boolean to the ExtensionState interface.

3. Update Extension State Context

In webview-ui/src/context/ExtensionStateContext.tsx:

• Add autoExpandEditDiffs to the state and context type
• Add a setter function setAutoExpandEditDiffs
• Handle the state message for the new setting

4. Modify ChatView.tsx to Auto-Expand Diffs

In webview-ui/src/components/chat/ChatView.tsx:

• Import the new setting from useExtensionState
• Modify the expansion logic to auto-expand diff rows when:
  • autoExpandEditDiffs is true
  • The message is a diff tool (editedExistingFile, appliedDiff, newFileCreated, searchAndReplace, insertContent)
• This can be done by initializing expandedRows for new diff messages based on the setting

5. Add UI Toggle (Optional Enhancement)

Add a toggle in the settings UI under an appropriate section (e.g., "Chat" or "UI" settings) to control this setting.

Technical Details

• The expansion state is managed in ChatView.tsx via expandedRows: Record<number, boolean>
• Diffs are rendered via CodeAccordian component which accepts isExpanded prop
• The setting follows the existing pattern used for other boolean settings like reasoningBlockCollapsed

This approach is non-breaking (defaults to current behavior), follows existing patterns in the codebase, and provides a simple VS Code native setting that users can easily discover and configure.

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.