feat(sdk-node): expose feature-gate config in Node SDK

[amilz]

Summary

Closes DEV-526.

• Adds enableFeatures, disableFeatures, and allFeatures to the napi SurfnetConfig, parsed via the existing parse_feature_pubkey() helper (kebab-case name, snake_case name, or base58 pubkey).
• Threads through new SurfnetBuilder::{enable_feature, disable_feature, feature_config} methods into SVM init.
• Builder default now seeds SvmFeatureConfig::default_mainnet_features() so single-feature overrides layer on a mainnet baseline instead of flipping every gate on (matches CLI semantics — previously, .enable_feature(X) would activate every known gate, not just X).
• Bumps @solana/surfpool to 1.3.0.

Usage

import { Surfnet } from '@solana/surfpool';

// Enable v1 transactions (SIMD-0385) on top of the mainnet feature baseline.
const surfnet = Surfnet.startWithConfig({
  enableFeatures: ['enable-loader-v4'],
  // Optional: also accepts base58 pubkeys, snake_case names,
  // or a top-level `allFeatures: true` to flip every known gate on.
});

console.log(surfnet.rpcUrl);
// ...send a versioned transaction, etc.

Unknown feature names reject at startup with an InvalidArg error listing the available gates.

Test plan

• cargo test -p surfpool-types --lib features — 22/22 pass
• cargo test -p surfpool-sdk --lib — 19/19 pass
• cd crates/sdk-node && npm run build && npm test — 6/6 pass (incl. new feature-gate case + invalid-name rejection)
• Follow-up: bump surfpool-sdk dep in @solana/kit-plugin-surfpool from ^1.2.0 → ^1.3.0 once published, and add a kit-tools V1-transaction test that fails without enableFeatures and passes with it.