fix: close database handles after failed open

[marcus-pousette]

Why

SQLite can return a database handle even when sqlite3_open_v2 fails, and requires callers to close it. The wrapper currently tracks that failed handle and throws before callers can release it, potentially leaving OPFS resources or locks alive. It also registers extension functions before confirming that the open succeeded.

SQLite documents the failed-open cleanup requirement in sqlite3_open_v2.

What changes

• Preserve the original open error before cleanup.
• Best-effort close a handle returned by a failed open and remove it from JavaScript tracking.
• Register extension functions only after a successful open.
• Add regression coverage proving the failed handle is closed, untracked, and never passed to extension registration.

Merge order

This PR is based on the upstream 1.1.1 sync in #4. Merge #4 first, retarget this PR to master, then use Create a merge commit. TreeCRDT #210 pins this exact head, so it must remain reachable from the default branch.