test: type-check Drive test sources

Problem

packages/drive/tsconfig.json checks src, examples, compile fixtures, and manual probes, but excludes ordinary test/**/*.test.ts and test/fixtures/**. Vitest strips types, so test API drift can stay invisible until a line happens to fail at runtime.

A diagnostic config including the full test tree currently reports roughly 50 errors. Examples include stale Effect APIs, unchecked indexed access, scope requirements, overly broad error unions, and fixture contract drift.

Proposed sequence

1. Add tsconfig.test.json and a typecheck:test script, but keep it out of required CI initially.
2. Fix errors in small file-scoped commits, starting with:
   • test/driver/index.test.ts
   • test/tool/producer.test.ts
   • test/instance/proxy.test.ts
   • test/tool/controller.test.ts
   • test/fixtures/**
3. Add typecheck:test to check once the diagnostic config is clean.

Done when

• Production and test TypeScript checks both pass.
• Script fixtures are covered, since start --script compiles them as user programs.
• Runtime test behavior and assertions remain unchanged.

Start with packages/drive/tsconfig.json and the existing scripts, then inspect the reported errors in test/driver/index.test.ts, test/tool/producer.test.ts, test/instance/proxy.test.ts, test/tool/controller.test.ts, and test/fixtures/**. Add the diagnostic test configuration and script, resolve the file-scoped type errors, and confirm production and test checks pass without changing runtime assertions.