CDP-5980: upgrade TypeScript to 6.0 and modernize tsconfig

[senechko]

Summary

• Upgrade TypeScript from 5.9.3 to 6.0.3 (native Go compiler support, stricter deprecation checks)
• Modernize tsconfig.json: replace deprecated moduleResolution: "node" with node16, remove unused baseUrl/paths, add explicit types: ["node"] (TS 6 no longer auto-includes @types/*)
• Bump @typescript-eslint/parser and @typescript-eslint/eslint-plugin to 8.60.0
• Align CI action versions in main.yml to v6 (matching publish.yml)
• Replace nyc with c8 for code coverage (merged from CDP-5980: replace nyc with c8 for code coverage #209) — c8 uses V8 native coverage; includes yargs@18 override for Node 26 compatibility

Test plan

• npm run build — tsc compiles without errors, output is CJS
• npm run lint — ESLint type-aware rules pass
• npm test — all 163 tests pass with 100% coverage (c8)
• CI green on Node 22, 24, 26
• Spot-checked dist/index.js — still emits CommonJS format

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​types/​node@​22.19.19 ⏵ 22.19.18
	typescript@​5.9.3 ⏵ 6.0.3	+1		+1

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[socket-security]

All alerts resolved. Learn more about Socket for GitHub.

This PR previously contained dependency changes with security issues that have been resolved, removed, or ignored.

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[Copilot]

Pull request overview

Toolchain-only upgrade that moves TypeScript from 5.9.3 to 6.0.3, modernizes tsconfig.json for Node16 module resolution, bumps @typescript-eslint to 8.60.0, and aligns CI action versions in main.yml with publish.yml. No lib/ runtime source is changed, so risk is confined to compile/lint/test/CI behavior; the published artifact remains CommonJS (no "type" field; module: node16 falls back to CJS emit when package.json is not ESM).

Changes:

• Upgrade TypeScript and related @typescript-eslint packages; regenerate lockfile.
• Modernize tsconfig.json: switch module/moduleResolution to node16, drop deprecated/unused alwaysStrict/baseUrl/paths, and add explicit types: ["node"].
• Bump actions/checkout and actions/setup-node to v6 in .github/workflows/main.yml to match publish.yml.

Reviewed changes

Copilot reviewed 2 out of 4 changed files in this pull request and generated no comments.

File	Description
tsconfig.json	Switches to node16 module/resolution, removes legacy options, pins explicit types: ["node"].
package.json	Bumps typescript to ^6.0.3 and @typescript-eslint/* to ^8.60.0.
package-lock.json	Regenerated lockfile reflecting the dependency bumps and transitive updates.
.github/workflows/main.yml	Updates actions/checkout and actions/setup-node from v4 to v6.

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[mike-engel]

@senechko can we go even further to typescript 7 here?

[senechko]

TypeScript 7 doesn't exist on npm yet — 6.0.3 is the latest major version. It's the one with the native Go compiler (tsgo) that the ticket references. We'll bump again when 7 lands.