fix(pm): key dispatch-gates' dropped-declaration probe on the derived marker roster

`POPULATION_MARKER_LOOKALIKE` was built from `POPULATION_MARKER_KEYS` alone
while the tool reads six reason-bearing keys, so `unparsedPopulationMarkers`
was a probe over three of them and a silence over the other three: a
`no-check-families`, `inherited-population` or `self-test-reads` line that
READS as a declaration and does not PARSE produced exactly what a file that
declares nothing produces.

The lookalike is now keyed on `Object.keys(MARKER_REASON_GRAMMARS)` — the
roster both grammar builders already derive — and each key's opener is the
forms ITS language has, so on `no-check-families` a lookalike is a `#`-form
line that fails to parse and a `//` line in a workflow stays document
content. The refusal prescribes `markerFormsFor(key)` rather than the whole
roster, so the remedy is one the author of that file can take.

Claude-Session: https://claude.ai/code/session_01Gqi43smmqjJ5sUrhfoPeKu
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude