perf(sqlite-native): remove delete file existence probe

[NathanFlurry]

Description

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Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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• My code follows the style guidelines of this project
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• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[NathanFlurry]

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This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• fix(rivetkit): surface native sqlite kv errors to callers #4645
• fix(rivetkit): prevent sleep races during disconnect and db work #4644
• fix(rivetkit): isolate engine envoys and propagate startup failures #4643
• test(rivetkit): remove wasm sqlite-only fixtures and coverage #4642
• chore(sqlite-vfs): remove wasm sqlite packages and workspace wiring #4641
• chore(rivetkit): remove wasm sqlite runtime #4614
• fix(sqlite-native): restore native startup kv preload #4639
• fix(sqlite-native): delete metadata before chunk range #4638
• fix(sqlite-native): keep truncate cache coherent #4637
• fix(sqlite-vfs): use delete range for truncate cleanup #4636
• fix(sqlite-native): restore kv error hook #4635
• perf(sqlite-native): avoid cloning cached read chunks #4634
• perf(sqlite-native): gate kv operation labels #4633
• perf(sqlite-native): reuse read cache for partial writes #4632
• perf(sqlite-native): remove delete file existence probe #4631 👈 (View in Graphite)
• fix(sqlite-native): gate native read cache behind env var #4630
• fix(pegboard): isolate runner config dc lookup failures #4625 : 1 other dependent PR (#4626 )
• docs(pegboard): note runner config upsert split write risk #4624
• fix(pegboard): unpack global runner config keys correctly #4623
• fix(pegboard-gateway): enforce tunnel message state #4622
• fix(pegboard-runner): clear terminal tunnel routes #4621
• fix(pegboard): skip protocol version keys in runner pool backfill #4620
• fix(pegboard): create missing normal runner configs #4619
• fix(epoxy): reuse cached optimistic value #4618
• main

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[claude]

PR Review: perf(sqlite-native): remove delete file existence probe

The optimization is sound for the common case: when a file exists, removing the kv_get existence probe before kv_delete_range saves one KV round-trip per delete. Since kv_delete_range is a no-op on an empty range, the probe was always redundant for that call.

Issue: WASM VFS parity not maintained

CLAUDE.md requires the native Rust VFS and WASM TypeScript VFS to match 1:1, including delete/truncate strategy. The WASM counterpart (rivetkit-typescript/packages/sqlite-vfs/src/vfs.ts) still performs the existence probe before deleting:

// rivetkit-typescript/packages/sqlite-vfs/src/vfs.ts:1395-1413
async delete(path: string): Promise<void> {
    const metaKey = getMetaKey(fileTag);

    // Get file size to check if the file exists
    const sizeData = await options.get(metaKey);  // still probing
    if (!sizeData) {
        return;  // returns without calling deleteRange or deleteBatch
    }

    await options.deleteRange(...);
    await options.deleteBatch([metaKey]);
}

This creates a behavioral divergence: for a non-existent file, the Rust VFS now unconditionally issues 2 KV calls (delete_range + kv_delete on the meta key), while the WASM VFS still issues only 1 (get on the meta key, then returns early). The same optimization should be applied to the WASM VFS in this PR to keep parity.

Minor note

For the non-existent-file case specifically, the change trades 1 KV read for 2 no-op KV writes. This is a minor regression on that path, but an acceptable trade-off if non-existent deletes are rare (e.g. SQLITE_OPEN_DELETEONCLOSE files that were always created). No action needed unless profiling shows otherwise.