## What
PR 3 of a stacked refactor of the SQL editor snippet state. Replaces the
two overlapping pieces of snippet lifecycle state — the `savingStates`
map (`IDLE|UPDATING|UPDATING_FAILED`) and the `isNotSavedInDatabaseYet`
boolean — with a single `SnippetStatus` enum.
## Status is attached at the data layer (never absent)
- `SnippetStatus` + `SnippetWithContent` now live in `data/content`. The
snippet queries attach `status: 'saved'` via a typed `withSavedStatus()`
helper, and `upsertContent` returns `SnippetWithContent` so move/rename
responses carry status too.
- A SQL-typed `getSqlSnippetById`/`useSqlSnippetByIdQuery` returns
`SnippetWithContent` (the generic `useContentIdQuery` stays for Reports,
which use it). `[id].tsx` loads content with **no casting**.
- `'new'` is attached on local creation (`createSqlSnippetSkeletonV2`).
## Behavior
Behavior-preserving for the existing auto-save flow (faithful mapping of
both old fields, including the replication-lag swallow). One incidental
fix: the read-only/saving indicator now also covers a brand-new
snippet's first save (previously only re-saves of persisted snippets had
distinct saving/failed states in some paths).
## Tests
New `sql-editor-lifecycle.test.ts` (29 tests) covering every predicate
and transition; existing rules tests updated. `pnpm --filter studio
typecheck` clean; 52 state/sql-editor unit tests pass.
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## Summary by CodeRabbit
## Release Notes
* **Refactor**
* Restructured SQL snippet persistence tracking, replacing boolean flags
with a comprehensive status system for clearer visibility into save
progress.
* Enhanced saving indicator UI to reflect accurate snippet save states.
* **Tests**
* Added test coverage for snippet persistence state transitions and
lifecycle scenarios.
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