Upgrade TypeScript 5.3.3 → 6.0.x

Tracking issue for upgrading the project's TypeScript compiler from 5.3.3 to the 6.0.x line.

This supersedes the Dependabot PR #1019, which could not be merged as a standalone version bump — TypeScript 6 requires coordinated changes to the lint toolchain, the compiler target, and the built dist/ output (see below).

Why the Dependabot PR couldn't merge as-is

1. Peer conflict with the old @typescript-eslint stack. On the previous lint toolchain, @typescript-eslint/eslint-plugin@8.48.0 declares peerDependencies.typescript: ">=4.8.4 <6.0.0", which hard-excludes TypeScript 6.0.3 and produces an ERESOLVE at install time.
2. Compiler target too old. The current tsconfig.json uses target: "es6". Modern TypeScript errors on the source as-is: TS1503: Named capturing groups are only available when targeting 'ES2018' or later. The build (ncc build ...) fails until the target is raised.
3. dist/ must be rebuilt. Raising the target changes the emitted/bundled output, so dist/setup/index.js and dist/cleanup/index.js must be regenerated and committed (the Check dist/ workflow enforces this).

Prerequisites

• chore: upgrade ESLint to v10 with flat config #1045 (ESLint v10 + flat config) must be merged first. It replaces the old @typescript-eslint/* packages with typescript-eslint@8.62.0, whose parser peer range is typescript: ">=4.8.4 <6.1.0" — this is the version that actually permits TypeScript 6.0.x. Without it, the upgrade hits the ERESOLVE peer conflict described above.

Work required (after #1045 lands)

• Rebase onto main (post-chore: upgrade ESLint to v10 with flat config #1045) and bump typescript ^5.3.3 → ^6.0.3 in package.json; regenerate package-lock.json.
• Raise the compiler target in tsconfig.json from es6 to at least ES2018 (recommend ES2022 to also unlock Error(msg, { cause }) and modern lib features). Reconcile lib/module settings as needed.
• Re-run npm run build and commit the regenerated dist/ (the bundle will change).
• Audit TypeScript 6.0 breaking changes against the codebase (stricter checks, removed/changed flags, lib differences). See the TypeScript 6.0 announcement.
• Confirm @typescript-eslint/typescript-eslint supports the chosen TS 6.0.x (peer is <6.1.0); bump if a newer line is needed.
• Re-run the full validation matrix: npm ci, npm run lint, npm run format-check, npm run build (verify dist/ matches), npm test, npm audit --audit-level=high.

Optional follow-up (enabled by the higher target)

• Once target is ES2022, adopt ESLint 10's preserve-caught-error rule (disabled in chore: upgrade ESLint to v10 with flat config #1045 for parity) by attaching { cause } to re-thrown errors (e.g. in src/distributions/graalvm/installer.ts).

Notes

• tsconfig.json is auto-synced from actions/reusable-workflows; coordinate the target change with upstream where applicable.
• Recommended sequencing: merge chore: upgrade ESLint to v10 with flat config #1045 → rebase → tsconfig target bump → rebuild dist/ → full validation.

Closes the effort tracked by #1019.