## Why
Changing an existing database from `FULL` to `INCREMENTAL` auto-vacuum requires a writer lock and can block pool initialization. SQLx also retries connection initialization failures, masking the original error as `PoolTimedOut`.
## What changed
Preserve existing auto-vacuum modes when opening writable pools, while continuing to initialize empty databases with incremental auto-vacuum. Return the first connection initialization error directly to the caller, retaining SQLx's normal error handling for later lazy connections.
## Testing
Add regression tests for fresh database settings, opening an existing `FULL` auto-vacuum database under a write lock, and preserving the WAL conversion lock error while allowing a subsequent open to succeed after the lock is released.
GitOrigin-RevId: b586c68e43a5a0d3b47268378716919d01b749cf
Benjamin Carlsson
c2d2f422e6