Fix Windows SQLITE_CANTOPEN by using native path format

[penalosa]

Summary

On Windows, SqliteDatabase::init() in sqlite.c++ constructs the database file path via Vfs::tryAppend(), which returns a kj::Path. The path was serialized with toString(), which is documented as the Unix-style serializer — it always produces forward-slash paths like D:/a/_temp/.../actor.sqlite.

This path is then passed to sqlite3_open_v2() with nullptr VFS, meaning SQLite uses the default win32 VFS which expects native Windows paths with backslashes.

The fix switches to toNativeString(true) which:

• On Windows: produces D:\a\_temp\...\actor.sqlite (via toWin32String)
• On non-Windows: is equivalent to toString() (no-op)

The tryAppend() codepath is also Windows-only (returns kj::none on other platforms), so this change is fully scoped to Windows.

Impact

This fixes SQLITE_CANTOPEN errors when using SQLite-backed Durable Objects with Miniflare on Windows. The error manifests at sqlite3_step() (line 1522) rather than sqlite3_open_v2() because the database opens successfully but WAL journal mode (PRAGMA journal_mode=WAL) fails when creating the .sqlite-wal and .sqlite-shm sidecar files.

Discovered while working on vitest-pool-workers v4 support in workers-sdk (cloudflare/workers-sdk#11632).

[codspeed-hq]

Merging this PR will degrade performance by 16.23%

❌ 1 regressed benchmark
✅ 69 untouched benchmarks
⏩ 129 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	jsonResponse[Response]	39.9 µs	47.6 µs	-16.23%

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_{Comparing penalosa/fix-windows-sqlite-path (64ba726) with main (fe9c1a6)²}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (1052d2e) during the generation of this report, so fe9c1a6 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩