## Summary
- The AI assistant's `create_notebook`/`update_notebook` tools could set
a `database_cell`'s `database_identifier` to a value that doesn't
correspond to any real database, because no tool exposes a project's
actual read-replica identifiers to the model.
- An unresolvable `database_identifier` silently breaks the cell:
`QueryEditor`'s connection-string lookup fails to find a match, and
running the cell fails with `Unable to run query: Connection string is
missing` — even though the exact same SQL runs fine when pasted into a
manually-created cell (which never sets this field).
- Fix: strip `database_identifier` from the agent-facing schema
(`agentCellSchema` in `notebook-schema.ts`) entirely, so the model can
no longer emit it at all. **This is a temporary fix** until we wire in
real read-replica support for the AI assistant (e.g. a tool exposing a
project's valid replica identifiers) — the field can be reintroduced
once the model has a legitimate source of truth to pull a valid
identifier from.
- Updated tests that relied on agent cells carrying
`database_identifier` to reflect the new behavior, and added a
regression test asserting `agentNotebookSchema` rejects a
`database_cell` with that field set.
Resolves FE-4224
## Test plan
- [x] `notebook-schema.test.ts`, `notebook-operations.test.ts`,
`notebook-tools.test.ts`, `AssistantNotebookPreview.test.tsx`,
`AssistantNotebookPreview.utils.test.ts` all pass
- [x] `tsc --noEmit` clean
- [x] Prettier clean on touched files
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Improved handling of database notebook cells when database metadata is
unavailable.
* Cells without database identifiers now display “No metadata” instead
of an incorrect replica identifier.
* Prevented invalid database identifiers from being accepted in
agent-generated notebook content.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Charis
717927f4f2