feat(kernel): consume published @databricks/databricks-sql-kernel napi packages (0.2.0)

[msrathore-db]

What

Declares the eight per-platform kernel binary packages as optionalDependencies, pinned to 0.2.0:

• @databricks/databricks-sql-kernel-{linux-x64-gnu,linux-arm64-gnu,linux-x64-musl,linux-arm64-musl,darwin-x64,darwin-arm64,win32-x64-msvc,win32-arm64-msvc}

Also refreshes native/kernel/README.md to drop the stale "M0 / not yet published" note.

Why

The kernel's per-platform napi packages are now published on npm (umbrella + 8 triples at 0.2.0). With them in optionalDependencies, a released @databricks/sql pulls the matching native binding from npm at install time instead of requiring a local npm run build:native. npm installs only the package matching the consumer's process.platform/process.arch; the others are skipped (that's what optionalDependencies tolerates), so installs on unsupported platforms keep working on the Thrift backend.

The committed native/kernel/index.js router + index.d.ts are unchanged — the driver still owns the type contract and just needs the .node binary, which now arrives via the optional dep.

Testing

Verified locally on darwin-arm64 against the published 0.2.0 binary (binding loads, version() → 0.2.0) with main's driver code:

SELECT 1 via kernel 0.2.0 (useKernel:true, PAT): [{"one":1}]

KERNEL_REV on main (0d46716) matches the 0.2.0 binding's exports (assertBindingShape passes).

⚠️ Follow-up before merge: regenerate package-lock.json

package-lock.json is not updated in this commit. The lockfile must be regenerated against public npm (the internal npm-proxy.dev.databricks.com does not mirror the @databricks/databricks-sql-kernel* scope yet — separate allowlist request in flight). Run with VPN off:

npm install --registry=https://registry.npmjs.org/
git add package-lock.json && git commit

CI's npm ci will be red until that lands.

This pull request and its description were written by Isaac.

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