## Context
Changes here adds a "Draft" state for notebooks with a new
`notebook-drafts` store - similar to how we handle query tabs in the
explorer.
This implies that if a user refreshes the tab while there's unsaved
changes to notebooks, the changes can be persisted locally and the user
will be able to continue from where they left off.
This also implies that If you create a new notebook (OR open an existing
notebook and make some changes) and refresh the browser, we no longer
show the native browser confirmation dialog about discarding changes.
We also reuse the existing confirmation dialog when saving a notebook if
its draft has diverged from the server side content - just updated the
language to be more generic rather than saying that the Assistant made
changes
<img width="429" height="238" alt="image"
src="https://github.com/user-attachments/assets/5c392aed-1633-4428-8060-28f495a01f04"
/>
Also fixes an unrelated issue - renaming a notebook should mark the
notebook as having unsaved changes (with the orange indicator)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
## Summary by CodeRabbit
* **New Features**
* Unsaved notebook edits are saved locally and restored when reopening
Studio.
* Drafts are scoped by project and protected from server changes through
conflict detection.
* Notebook tabs indicate unsaved changes, including drafts from unsaved
notebooks.
* **Bug Fixes**
* Closing a tab with local edits prompts for confirmation and removes
its saved draft.
* Notebook save state reflects the server-confirmed update time.
* Conflict messages clearly describe changes made on the server.
* **Style**
* Improved keyboard focus behavior for tab controls.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Joshen Lim
a1686025b6