feat(typescript): exactOptionalPropertyTypes + export surface restructure

[dean0x]

Summary

Complete the TypeScript surface cleanup: enable exactOptionalPropertyTypes in tsconfig.base.json, restructure the published export surface at packages/mds/src/node.ts, evaluate TypeScript 7 compatibility, and address pre-test build stale-dist hazard.

Deferred Issues

From review [wave-v0.4.0-wave1/2026-08-19_1216]:

Finding	File:Line	Reason
architecture-04	packages/mds/src/node.ts:348	Restructuring the published export surface at the tag.
typescript-06	tsconfig.base.json	exactOptionalPropertyTypes would fire across every package simultaneously.
testing-07	packages/mds/package.json:42	CI verified safe; local-only stale-dist hazard.
dependencies-05	packages/mds/package.json:42	Accurate observation, not a defect; the TS 7 evaluation is v0.5.0.
dependencies-06	packages/mds/package.json:22	Lowering the type floor could surface diagnostics across every package pre-tag.

Acceptance Criteria

• Enable exactOptionalPropertyTypes (may require surface adjustments)
• Deduplicate export lists in node.ts and across packages
• Evaluate TS 7 compatibility and document findings
• Add pretest build step to catch dist stale issues
• Consider lowering type-checking floor (if safe)

Related

• PR v0.4.0 Wave 1: breaking changes, live-bug fixes, and release-safety gates #308 (wave/v0.4.0-wave1)

For v0.5.0