feat(chat): Improve diff appearance in main chat view

[hannesrudolph]

This PR improves how edits are displayed in the main chat view:

Before	After

Scope: UI-only presentation improvements for diffs and counters; no changes to tool behavior.

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Important

Enhances chat view diff display with unified diffs, inline stats, and new rendering components.

• Behavior:
  • Improves diff appearance in chat view by using unified diffs and displaying inline diff stats.
  • Adds DiffView component for rendering diffs with line numbers and highlights.
  • Updates ChatRowContent to handle new diff stats and display them.
• Utilities:
  • Adds computeDiffStats, sanitizeUnifiedDiff, and convertNewFileToUnifiedDiff functions in stats.ts for diff processing.
  • Implements parseUnifiedDiff in parseUnifiedDiff.ts to parse unified diff strings.
• UI Components:
  • Updates CodeAccordian to display diff stats and use DiffView for diff rendering.
  • Modifies BatchDiffApproval and ChatRow to incorporate new diff handling.
• Testing:
  • Adds ChatRow.diff-actions.spec.tsx to test diff stats display in ChatRowContent.

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[roomote]

Rooviewer   See task on Roo Cloud

All previously flagged issues have been resolved. No new issues found in the latest commits.

Issues to Fix

• Incorrect line counting for new files (ChatRow.tsx:472-481): The special case for newFileCreated counts all lines in the unified diff format (including headers like --- /dev/null, +++ filename, @@ ...), resulting in inflated counts. The computeDiffStats function already correctly handles unified diffs - remove the special case and use it consistently.
• Hardcoded white color breaks light theme (DiffView.tsx:230): The +/- indicators use hardcoded #ffffff which will be invisible against light backgrounds. Use a theme-aware color variable instead.
• Redundant no-op replacements in stripCData (diffUtils.ts:59-63): The case-insensitive replacements on lines 59 and 62 already remove both HTML-encoded and raw CDATA markers, making the subsequent case-sensitive replacements on lines 60 and 63 no-ops. Remove lines 60 and 63 to eliminate the CodeQL warning.

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Previous reviews

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[Copilot]

Pull Request Overview

This PR introduces a new DiffView component to render unified diffs with VSCode-style formatting, and enhances the UI to display diff statistics (+/- line counts) for file operations. The changes improve the visual presentation of code changes across the application.

• Adds a DiffView component for rendering unified diffs with side-by-side line numbers
• Implements diff stats computation and display for file edit operations
• Converts SEARCH/REPLACE and new file formats to unified diff format

Reviewed Changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
webview-ui/src/components/common/DiffView.tsx	New component to render unified diffs with VSCode styling
webview-ui/src/components/common/CodeAccordian.tsx	Adds diff stats display and integrates DiffView for diff language
webview-ui/src/components/chat/ChatRow.tsx	Computes diff stats and converts various diff formats to unified diff
webview-ui/src/components/chat/BatchDiffApproval.tsx	Adds diff stats computation and SEARCH/REPLACE conversion
webview-ui/src/components/chat/tests/ChatRow.diff-actions.spec.tsx	New test file for diff stats functionality
webview-ui/src/components/chat/ChatView.tsx	Comment clarification update
webview-ui/package.json	Adds diff library dependencies
pnpm-lock.yaml	Lockfile updates for new dependencies

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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[roomote]

One issue has been resolved, but the hardcoded white color issue remains. Please address the remaining issue before approval.

[hannesrudolph]

Addressed remaining review item: replaced hardcoded #ffffff with theme foreground for +/- indicators in DiffView.tsx. All CI checks are green on the latest run. The github-advanced-security entry posted a blank comment and CodeQL is passing; there are no actionable security findings attached to this PR right now.

[roomote]

One issue has been resolved (hardcoded white color), but there is still one outstanding issue to address: incorrect line counting for new files in ChatRow.tsx.

[hannesrudolph]

Resolved the CodeQL warning shown in your screenshot. Updated stripCData() to: (1) convert HTML-encoded CDATA markers to raw, then (2) strip raw markers. This removes the no-op replacement flagged by CodeQL. Changes around lines 58-64.

[roomote]

Review complete. One issue found that needs to be addressed before approval.

[hannesrudolph]

fix(webview-ui): Correct new-file diff line counting by ignoring trailing newline in unified diff; added a unit test to cover this behavior.
Key changes:

• webview-ui/src/utils/diffUtils.ts (convertNewFileToUnifiedDiff)
• webview-ui/src/components/chat/tests/ChatRow.diff-actions.spec.tsx
• All webview-ui tests pass locally (vitest). Ready for re-review.