chore: bump napi to 3.12.2 alongside napi-derive 3.6.3

[BartWaardenburg]

Supersedes #116. That PR bumped napi-derive to 3.6.3 and napi-build to 2.4.1 but left napi at 3.12.0, so the macro emitted symbols the pinned runtime does not have and every Check job failed:

error[E0433]: cannot find `NativeBorrowScope` in `bindgen_prelude`
error[E0433]: cannot find `NativeBorrowBarrier` in `bindgen_prelude`
error[E0425]: cannot find function `register_native_borrow_with_value` in module `napi::bindgen_prelude`

napi and napi-derive are both pinned as "3" in the workspace manifest, so Dependabot files them as separate lockfile-only updates and can split a pair that has to move together. This moves the whole set: napi 3.12.0 to 3.12.2, napi-derive 3.6.2 to 3.6.3, napi-derive-backend 6.1.1 to 6.1.2, napi-build 2.4.0 to 2.4.1.

Local gate: cargo check --workspace --all-targets, cargo test --workspace, and cargo clippy --workspace --all-targets -- -D warnings all green.

[codspeed-hq]

Merging this PR will regress 1 benchmark

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
❌ 1 regressed benchmark
✅ 183 untouched benchmarks
⏩ 76 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	fallow_cloud_coverage srcmap NAPI individual lookup	133.3 ms	157.5 ms	-15.38%
⚡	real_world_lookup_single[Preact] srcmap WASM buf	181.2 µs	72.2 µs	×2.5
⚡	real_world_lookup_single[Preact] srcmap WASM flat	231.9 µs	121 µs	+91.6%
⚡	real_world_lookup_single[Preact] source-map-js	832.3 µs	724.9 µs	+14.82%
⚡	lookup_single_original_position_for	1.4 µs	1.3 µs	+10.3%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing chore/napi-lockstep (9e6bcaf) with main (1030171)²}

Footnotes

1. 76 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 (9372537) during the generation of this report, so 1030171 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩