HUD/CI: test files (tests/**) are transpile-only and outside tsconfig `include` — TS regressions in tests escape CI

[dean0x]

Problem

`tsconfig.json` scopes `include` to `src/cli/`, and vitest transpiles tests via esbuild without type-checking. As a result, TypeScript regressions inside `tests/` are not caught by `npm run build` or CI.

Evidence

Surfaced during code review of PR #254 (chore/devflow-fine-tuning):

• Reviewer: typescript reviewer
• Confidence: 90%
• Classification: pre-existing / out-of-blast-radius (Triager verdict)

Scope

This is a pre-existing, project-wide CI/tsconfig concern unrelated to PR #254's four-tweak purpose. Fixing it would require a project-wide tsconfig or CI change, so it was deferred to its own ticket rather than expanded into that PR.

Suggested Approaches

1. Add a `typecheck:tests` script: `tsc --noEmit -p tsconfig.test.json` covering `tests/**`, wired into CI
2. Widen the existing tsconfig.json `include` to cover both `src/cli/` and `tests/`

Related

Relates to PR #254 (chore/devflow-fine-tuning)