Fix Windows test isolation and cleanup

[brandonkramer]

Summary

• isolate storage-backed tests with PI_SCRAPER_STORAGE_ROOT instead of HOME, including both tool-smoke suites
• await closeStorageDbs() before deleting temporary roots and add missing closes in crawl/result tests
• make the remaining path and permission assertions portable on Windows
• scope download-test cleanup to its fixture directory
• run the full test suite in the Windows CI job

Why

On Windows, node:os.homedir() ignores test-only HOME overrides, so smoke and storage tests could write under the real user profile. Several teardowns also started the asynchronous database close without awaiting it, then immediately deleted SQLite/WAL files, causing EBUSY failures.

Impact

Test storage is now isolated to per-test temporary roots, SQLite handles are closed before cleanup, and Windows CI covers the same full suite used on Linux. Production runtime behavior is unchanged.

Validation

• bun run test on Windows: 105 files passed; 916 tests passed, 5 intentionally skipped
• bun run typecheck
• bun run lint (passes; existing warnings remain)
• bun run format:check
• bun run test:selection: 16/16
• bun run test:tools: 7/7
• bun run lint:workflows
• git diff --check
• read-only Cursor review; its one actionable cleanup-target finding was fixed before publication

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