## Summary
- **Fixes #2396**: When creating a new chat (including "summarize to new
chat"), the system was hardcoding `ref: "main"` when getting the
`initialCommitHash`, causing issues when users work on feature branches
- Changed to use the default `"HEAD"` ref instead, so the chat correctly
tracks the currently checked-out branch's commit
- This prevents merge conflicts and ensures changes are applied to the
correct branch

## Test plan
1. Create a feature branch from main
2. Create a new chat while on the feature branch
3. Verify the new chat tracks the feature branch's commit, not main's
commit
4. Test "summarize to new chat" functionality while on a feature branch

🤖 Generated with [Claude Code](https://claude.com/claude-code)
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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk: a small, localized change that only affects which git ref is
used to capture `initialCommitHash` during chat creation.
> 
> **Overview**
> When creating a new chat, the `initialCommitHash` is now resolved from
the repo’s current `HEAD` rather than forcing `ref: "main"`, so chats
created on feature branches track the correct starting commit.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
541b373218a04781d63dfdb05474b4f110d38ab0. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
New chats now use the currently checked-out branch (HEAD) to resolve
initialCommitHash instead of hardcoding main. This ensures chats track
the correct branch and prevents merge conflicts. Fixes #2396.

<sup>Written for commit 541b373218a04781d63dfdb05474b4f110d38ab0.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>