[TomyCesaille]

Closes #15.

GitLab (prtop/forges/gitlab.py): on ci_must_pass, the status comes from head_pipeline.status in the merge request _hydrate already fetches. No extra call.

• failed reads as ❌ CI failed, canceled and canceling as 🛑 CI canceled, and a missing pipeline as 💤 no pipeline. All three are marked !.
• created, scheduled and the running statuses read as ⏳ CI running, marked .. GitLab reports a pipeline that is still running as ci_still_running, so these cover a pipeline about to start.
• Any other status, such as manual or skipped, shows as ❔ pipeline <status>, marked ?, like any state prtop does not map.

GitHub (prtop/forges/github.py): it had the same gap. A blocked pull request whose required checks report FAILURE or ERROR now reads as ❌ CI failed, marked !. EXPECTED, a required check that has not reported yet, stays CI running: GitHub cannot tell a check about to start from one that never will.

• CI must pass leaves the vocabulary (model.CI_MUST_PASS).
• ❌ keeps a single meaning, a run that failed, now in three scopes. test_a_glyph_never_carries_two_meanings_in_the_status_column lists model.CI_FAILED beside the two deploy states.
• examples/claude-code/commands/prs.md tells an agent what to do with each new status, with the glab and gh calls. It reads the failed job's log, fixes what the change broke or retries a flaky job, retries a canceled pipeline, and starts a missing one.

Docs: AGENTS.md's conventions ask every pull request that changes what a user sees or runs for its CHANGELOG.md line, under [Unreleased], in the same pull request. Until now only CONTRIBUTING.md said so. CHANGELOG.md gets back the blank line after ### Changed.