chore(deps): adopt TypeScript 6

[drewstone]

Moves repository compilation to TypeScript 6.0.3, the newest version supported by the current declaration bundler. Removes one test-suite timeout source by running three independent claim-grounding arms concurrently.

Checks: 466/466 executed tests; build and declarations; typecheck; lint 185/185 files; clean package install and 5 exported imports. TypeScript 7 was tested and rejected because upstream rollup-plugin-dts crashes during declaration generation.

[tangletools]

✅ Auto-approved drewstone PR — 34304400

This PR was opened by the trusted drewstone account.
The full PR reviewer audit still runs separately and will publish findings if it detects issues.

_{tangletools · auto-approval · reason: drewstone_author · 2026-07-25T01:29:04Z}