fix(web): fix scroll position for references further down in a file

[brendan-kellam]

Summary

• Replaces coordsAtPos() with view.lineBlockAt() to get line positions from CodeMirror's internal height map
• Also uses codeMirrorRect for coordinate calculation instead of relying on coords.top from the potentially-unrendered line
• Fixes scrolling to references in lines that haven't been rendered yet by CodeMirror's virtualizer

Test plan

• Open a chat and select a file reference that points to a line near the top of a file — scroll position should be correct
• Select a file reference that points to a line further down in a large file — scroll position should now correctly land on the target line

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Fixed scroll positioning in the chat interface when selecting references that target lines located further down in a file. The viewport now correctly centers the referenced line for improved visibility and navigation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: d24635cc-bd96-4c5f-9d6c-4b6f5bae2ffd

📥 Commits

Reviewing files that changed from the base of the PR and between c7ee456 and 67e3ca1.

📒 Files selected for processing (2)

• CHANGELOG.md
• packages/web/src/features/chat/components/chatThread/referencedSourcesListView.tsx

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Walkthrough

This pull request fixes scroll positioning in the chat UI when selecting chat references that target lines located further down in a file. The CHANGELOG documents the fix. The implementation replaces scroll coordinate calculation in referencedSourcesListView.tsx to use CodeMirror's document layout API instead of the previous coordinate method.

Changes

Cohort / File(s)	Summary
Documentation CHANGELOG.md	Added Unreleased → Fixed entry documenting scroll position fix for chat reference selection (#1036).
Chat Reference Scroll Logic packages/web/src/features/chat/components/chatThread/referencedSourcesListView.tsx	Replaced scroll positioning mechanism to use CodeMirror document layout (lineBlockAt().top) and DOM bounding rectangles instead of coordsAtPos(), computing scroll position to center the target line.

Possibly related PRs

• fix(web): fix inaccurate scroll position when selecting chat references #1035: Modifies the same scroll-to-selected-line logic in referencedSourcesListView.tsx using an alternative approach to fix scroll positioning.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: fixing scroll position for chat references pointing to lines further down in files, which matches the core bug fix implemented in the pull request.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch brendan/fix-chat-reference-scroll

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