docs(skill): point the finish-release opencode gate at a check that exists

[David Koleczek (DavidKoleczek)]

Phase 4 of amplifier-agent-finish-release-process instructed the runner to
verify the amplifier-app-opencode floor bump with:

uv run pytest tests/test_version.py tests/test_prereqs.py -q

Neither file exists. Both were removed in that repo's PR #21, which retired its
entire unit-test layer in favour of spec-as-contract e2e coverage:

tests/test_host_config.py    tests/test_modes_bridge.py
tests/test_onboarding.py     tests/test_platform_utils.py
tests/test_prereqs.py        tests/test_skills_bridge.py
tests/test_version.py

So the command errors with file or directory not found, no tests run, and the
phase that is supposed to catch a wrong floor verifies nothing. This surfaced
while cutting 0.15.1, where the step could not be performed as written.

Change

Point the step at make check, which is that repo's real fast gate (ruff lint
and format), and follow it with a read-back of the three constants.

The read-back is not decoration. make check accepts any string, so a typo'd
or stale MIN_AGENT_VERSION passes lint cleanly and then fails on a user's
machine at install time — that constant drives a forced reinstall and names the
exact git tag the launch-time self-heal installs. Reading the values back and
comparing them to the tag just pushed is the only thing in the phase that
actually checks the number.

What this deliberately does not do

• No unit tests are restored. Removing them was an intentional
  restructuring in that repo, not an accident to undo from here.
• No e2e suites are invoked. They require a DTU and cost minutes, which does
  not belong in this step. They would not help regardless: the onboarding suite
  pins its fake agent to 99.0.0 specifically so it does not track the floor,
  and the only two references to these constants under tests/ are a comment
  and a docstring, not assertions.

The replacement commands were run against amplifier-app-opencode rather than
assumed correct.

🤖 Generated with Amplifier