build(deps-dev): bump TypeScript to 6.0.3

[helly25]

Upgrade the VSCode extension to TypeScript 6.0.3, the highest stable release accepted by the current lint toolchain. This advances the compiler safely while TypeScript 7 remains blocked by typescript-eslint's declared peer range.

AG;DR

Implementation

• Bump typescript from ^5.9.3 to ^6.0.3 and refresh its lockfile entry.
• Explicitly load Node ambient types for extension compilation, as required by TypeScript 6.
• Explicitly load Node and Mocha ambient types for runtime-test compilation.

Validation

• npm install --no-audit --no-fund
• npm run compile
• npm run compile-test
• npm test (66 tests passed)
• pre-commit run --files extension/package.json extension/package-lock.json extension/tsconfig.json extension/tsconfig.test.json
• npm audit --package-lock-only --json reports the same two existing transitive development-tool findings as main; this bump adds no advisory.

Portability

The explicit node and mocha type packages are existing development dependencies and make compiler behavior deterministic under TypeScript 6.

Dependencies

This branch is based on current main. It provides the safe portion of #151 while that TypeScript 7 update remains incompatible with @typescript-eslint/eslint-plugin@8.71.0.

Limitations

Local npm run package passed TypeScript compilation but could not build the WASM bundle because the local Homebrew Rust sysroot lacks wasm32-unknown-unknown. Pull-request CI installs the repository-declared Rust toolchain and supplies the authoritative runtime and VSIX package checks.

This change does not enable TypeScript 7; that requires a future typescript-eslint release whose peer range includes it.