test(cli): smoke-test the built CLI against a fixture scaffold

[abhinav-phi]

Resolves #57.

What

A smoke suite that spawns the built dist/cli.js in a temp project and asserts exit codes and output for the commands a user or agent reaches for first:

• --version — strict equality against package.json's version
• log → timeline → timeline --json — one event rendered end to end in both output modes
• check and check --json — healthy fixture reports 100/100, JSON is parseable with the documented shape
• heartbeat, doctor — run clean on the fixture
• --help — lists the top-level commands

Fixture

Each test gets a fresh temp project with a minimal .mex/ scaffold: ROUTER.md plus an AGENTS.md tool anchor — the state mex setup leaves behind. The anchor matters: without it, check reports SCAFFOLD_ORPHANED (exit 1), which is correct product behavior and exactly the kind of drift the smoke test should be able to express, not fight.

Why this would have caught the shipped bugs

The two version regressions shipped because CI exercised library code and the packed install, but never ran the real CLI against a scaffold inside the suite. I verified the detection property directly: injecting a hard-coded VERSION = "0.7.0" into the bundle (reproducing the original hard-coded-literal bug) makes the --version test fail with expected '0.7.0' to be '0.8.0'. CI already runs npm run build before npm test, so the suite has the bundle it needs; the test also fails with an explicit message if dist/cli.js is missing.

No production code is touched — test + fixture only.

[abhinav-phi]

@theDakshJaitly @theyashasvipandey — status: everything on this PR is done and green. Rebased-clean against current main (no conflicts: test/cli.test.ts and the packed-CLI smoke step coexist with these 7 spawned-CLI checks — CI confirms), all checks pass (check 22.22.0/24, hub-browser, release-performance, storage-portability macos+windows).

For reviewers: the suite spawns the built dist/cli.js against a fixture scaffold (.mex/ROUTER.md + AGENTS.md anchor) covering --version (strict equality with package.json — mutation-verified: injecting a hard-coded 0.7.0 into the bundle makes the test fail), log→timeline end-to-end in both output modes, check/check --json, heartbeat, doctor, and --help. CI builds dist via npm ci before npm test, so the bundle is there. Requesting a review when you get a chance 🙏