fix(scripts): the required-context self-test proves WIRING with invocations, not prose (#10877)

Two presence assertions in `--self-test` decided "is this wired up?" from text a
comment, a label or an `echo` could supply. Both error toward a silent GREEN —
the gate reporting that a required-context pin runs when it does not.

- the `lint` job block carried a second `/^\s*#/` line filter and matched
  `/run: pnpm check:required-contexts\b/` over a raw text slice. It is now a
  structural read of `jobs.lint.steps`. The slice was also bounded by
  `'\n  typecheck:'`, which is not the job after `lint:` — measured, it covered
  five jobs.
- the caller sweep's single equality was two assertions in opposite directions
  sharing one WIDE recognizer. Split: the absence half keeps `wiresLiveRead`,
  the presence half gets `invokesLiveRead`.

The two recognizers are deliberately different widths and are pinned together,
including one case where they disagree by design.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DdCnBGcHeufjrq7drTD3wt

Author: claude