skill-quality: amend check 12 to accept a populated when_to_use, sequenced behind #1096

[kyle-sexton]

This was generated by AI during work-loop execution.

Why this exists

Split out of #1404 item 3 (PR #1450 implemented items 1, 2, and 4 from that issue; item 3 was
explicitly out of scope there because the issue itself sequences it behind this repo's #1096).

The fix

plugins/skill-quality/scripts/check-skill.sh check 12 (currently around lines 440-448) warns unless
the literal text use when appears in description or when_to_use. A skill that puts bare
single-quoted trigger phrases in when_to_use with no prose marker still warns — measured at 15 of 15
on a prepared rewrite block during the #1271 listing-budget measurement.

Two fixes were identified, and they are not equivalent:

• Keep a literal Use when: prefix inside when_to_use. No code change, but it costs roughly ten
  characters per skill on top of the description/when_to_use joiner's three (skill-quality: check-skill.sh has no shared listing-budget check, plus three smaller gate defects #1404 item 2, already
  fixed) — across ~130 model-invocable skills, about +1,700 characters, which is more than the entire
  recoverable mass the skill metadata: trigger phrases crammed into description; when_to_use is unused and the shared listing budget silently drops them #1271 measurement found.
• Amend check 12 to accept a populated, single-quoted when_to_use as satisfying the trigger-spec
  requirement. This is the better fix: the warning text ("a description is a trigger spec, not a
  summary") encodes the pre-when_to_use authoring model, and when_to_use exists precisely to let a
  skill state its triggers without also needing a redundant prose Use when: prefix.

Why this is sequenced, not just picked up now

#1096 ("feat(skill-quality): fresh-eyes delegation doctrine + conformance gate (check 21)") is a real,
currently open, active PR (branch feat/fresh-eyes-delegation-doctrine-gate, ~708 additions) that
edits check-skill.sh — appending check 21 at the end of the file, just before the summary block.
Confirmed via gh pr view 1096 / gh pr diff 1096 at the time #1450 was authored: no PR yet exists
for check 12 specifically, and check 12's region (~lines 440-448) does not literally overlap #1096's
appended block, so there is no hard merge conflict — but #1404's own text explicitly sequences this
item behind #1096, and #1450 preserved that sequencing rather than overriding the issue author's
stated intent.

Pick this up once #1096 merges (or is closed/abandoned) — re-verify #1096's state before starting,
since both this file's check-12 region and #1096's own check-21 region are still fair game.

Acceptance criteria

• check-skill.sh check 12 accepts a populated, single-quoted when_to_use (i.e. a nonempty
  skill_frontmatter::extract_triggers result over description+when_to_use) as satisfying the
  trigger-spec requirement, without also requiring a literal Use when: string.
• Existing check-12 tests in check-skill.test.sh (e.g. "unquoted Use when: triggers warn") keep
  passing; add a new fixture proving a populated when_to_use with single-quoted triggers and NO
  Use when: prose no longer warns.
• Dogfood check-skill.sh against a representative marketplace skill using bare when_to_use
  triggers to confirm the warning clears.
• #1096 is merged, closed, or otherwise confirmed no longer touching check-skill.sh before this
  is claimed.

Related

Refs #1404 (source item; #1450 closed items 1/2/4 there).
Refs #1096 (blocking — sequence behind it).

[kyle-sexton]

This was generated by AI during work-loop execution.

Blocked — not claimed

The dispatched worker verified prerequisite PR #1096 is still open/unmerged, matching this
item's own title ("sequenced behind #1096"), and correctly declined to claim or implement
against an unstable base. Applying needs-human now so this doesn't resurface on the
autonomous frontier every cycle — same label-gap pattern already fixed once this session on
#1269. Re-entry condition: PR #1096 merges.