fix(ui): keep mention highlights after slash command expansion

[marius-kilocode]

Rendered user messages color inline @mentions by using source offsets from attachments. When a slash command expands or rewrites the displayed text before an attachment mention, those offsets can become stale and highlight unrelated words instead of the actual mention.

This change moves message highlight segmentation into a focused helper that first verifies the stored range still matches the original source value. If the range is stale, it relocates the highlight by the source value in the rendered text, while preserving the existing regex fallback for plain path mentions. This keeps @git-changes and other attachment mentions visually aligned with the text the user sees after command expansion.

Prompt:

Before:

After:

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (5 files)

• .changeset/fix-slash-mention-highlight.md
• packages/kilo-ui/src/components/message-highlight.test.ts
• packages/kilo-ui/src/components/message-highlight.ts
• packages/kilo-ui/src/components/message-part.tsx
• packages/kilo-vscode/tests/unit/kilo-ui-contract.test.ts

Previous Review Summaries (2 snapshots, latest commit 3219a06)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit 3219a06)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• packages/kilo-ui/src/components/message-highlight.test.ts
• packages/kilo-ui/src/components/message-highlight.ts

Previous review (commit ff427e5)

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	1
SUGGESTION	0

Fix these issues in Kilo Cloud

Issue Details (click to expand)

WARNING

File	Line	Issue
packages/kilo-ui/src/components/message-highlight.ts	46	Relocating stale refs with indexOf(source.value) always picks the first duplicate mention, so repeated identical mentions collapse onto the first highlight.

Files Reviewed (4 files)

• .changeset/fix-slash-mention-highlight.md - 0 issues
• packages/kilo-ui/src/components/message-highlight.test.ts - 0 issues
• packages/kilo-ui/src/components/message-highlight.ts - 1 issue
• packages/kilo-ui/src/components/message-part.tsx - 0 issues

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_{Reviewed by gpt-5.4-20260305 · Input: 48.8K · Output: 6.1K · Cached: 194.6K}

_{Review guidance: REVIEW.md from base branch main}