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

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

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

How Has This Been Tested?

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Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• 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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• chore(engine): publish engine bases in ci #4649
• chore: lockfile lefthook #4647
• 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. Removing the kv_get existence probe before kv_delete_range saves one KV round-trip per delete in the common case where a file exists. Since kv_delete_range is a no-op on an empty range, the probe was redundant. The change is correct and safe.

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 (lines 1395-1413):

async delete(path): Promise<void> {
    const metaKey = getMetaKey(fileTag);
    const sizeData = await options.get(metaKey);  // existence probe
    if (!sizeData) return;  // short-circuit
    await options.deleteRange(...);
    await options.deleteBatch([metaKey]);
}

The same optimization should be applied to the WASM VFS in this PR to keep the two implementations in sync. Right now they diverge: the native Rust VFS unconditionally deletes, while the WASM VFS probes first and short-circuits. This could lead to subtly different observable behavior, for example different error propagation when the meta key is absent but chunk keys exist from a partial write.

Minor: extra KV round-trip when file never existed

When the file does not exist, the new code issues two KV ops (range delete + meta delete) instead of the one probe the old code issued. This is unlikely to matter in practice since SQLite xDelete is normally only called on existing files, but it is a slight regression for that edge case.

Summary

The optimization is valid and the code is correct. The main concern is the divergence from the WASM VFS. packages/sqlite-vfs/src/vfs.ts should be updated to match (remove the get probe, always issue deleteRange + deleteBatch) to satisfy the CLAUDE.md 1:1 parity requirement.