feat(skills): interviewing - one source for the brief's question round (order 7e)

/trekbrief Phase 3 carried the interview form inline. It now asks for the
new skill voyage:interviewing by name (allowed-tools gains Skill) and keeps
only its own contract: the size class and budget, the three fixed questions
(framing first, class, storage), where each answer lands in the brief, and
the answers that decide nothing. Step 3a and the form points of Step 3c move
into the skill with their credits (Pocock, Osmani, Spec Kit; licences and
line ranges checked at the pinned commits).

Red baseline first (3 helper interviews against a fixed answer sheet,
Opus 5.5): 10-11 questions in round 1 (3 of 3), 15 of 31 without a
recommendation, a hollow answer written in as a decision (2 of 3), unasked
scope as a requirement (2 of 3). With the skill: 4, 0 of 12, 0 of 3, 0 of 3.
Fact questions and stopping did not fail without it.

Also: pointers to voyage:writing-criteria (S3) where criteria are asked and
written, both review skill names (S3 + S4) in the brief-reviewer prompt; the
intent pins that read moved text now read the skill, same assertions; the
Phase 7 line_ref moves with the shorter Phase 3; 7 eval cases (3/2/2).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -160,7 +160,9 @@ Interactive requirements-gathering command. Runs a **question round sized to the
 
 **Ceremony by size.** The task is put in one of three classes, `small`, `bounded` or `architectural` (the heaviest when in doubt), said aloud, overridable by you, and only ever moved up when the task proves bigger. The class sets the question budget (a `small` task: at most 4 questions, in one round) and the review cap, and is written to the brief as `ceremony:`.
 
-**The question round.** Facts are looked up in the repo, never asked. Every question that can be answered now is asked at once, the recommended answer first, ranked by impact × uncertainty; what the budget leaves out is on a visible Deferred list, and what can be predicted is written down as an assumption you see before approving. A hollow answer ("sounds good", "do as you like") or an empty one decides nothing.
+**The question round.** The round runs in the form of the `voyage:interviewing` skill, which `/trekbrief` asks for by name. Facts are looked up in the repo, never asked. Every question that can be answered now is asked at once, at most four per question call, one decision each, the recommended answer first, ranked by impact × uncertainty; what the budget leaves out is on a visible Deferred list, and what can be predicted is written down as an assumption you see before approving. A hollow answer ("sounds good", "do as you like") or an empty one decides nothing. `/trekbrief` adds its own part: the three fixed questions (framing, size class, where the brief is stored), the budget per class, and where each answer lands in the brief.
+
+Success criteria are proposed in the form of `voyage:writing-criteria`, so the review can run them, and `brief-reviewer` is told to judge by that skill and by `voyage:reviewing-adversarially`.
 
 Then `brief-reviewer` scores the draft on six dimensions (completeness, consistency, testability, scope clarity, research-plan validity, memory alignment) and gates publication, up to 1 / 2 / 3 review iterations by class; force-stop yields a `brief_quality: partial` brief with the failing dimensions documented.
 
@@ -168,7 +170,7 @@ Then `brief-reviewer` scores the draft on six dimensions (completeness, consiste
 
 Output: `.claude/projects/{YYYY-MM-DD}-{slug}/brief.md`
 
-Borrowed, with credit: size classes and the ratchet from obra/superpowers (MIT), the class ladder from Kiro's docs (idea only), the round from mattpocock/skills (MIT), the budget and Deferred list from GitHub Spec Kit (MIT), the stop rule and hollow answers from addyosmani/agent-skills (MIT), the hash-chained log from bashebr/ai-native-sdlc (MIT). Pinned commits in `commands/trekbrief.md` Phase 3 and `lib/util/approval-log.mjs`.
+Borrowed, with credit: size classes and the ratchet from obra/superpowers (MIT), the class ladder from Kiro's docs (idea only), the round from mattpocock/skills (MIT), the budget and Deferred list from GitHub Spec Kit (MIT), the stop rule and hollow answers from addyosmani/agent-skills (MIT), the hash-chained log from bashebr/ai-native-sdlc (MIT). Pinned commits in `commands/trekbrief.md` Phase 3 (the classes), `skills/interviewing/SKILL.md` (the round) and `lib/util/approval-log.mjs`.
 
 ### Modes
 
@@ -651,6 +653,7 @@ model. A skill is advice; each one says which check stands behind it, or "prose
 |---|---|---|---|
 | `voyage:test-first` | Red before green: the repo's own test command, a test seen failing on an assertion (a crash is not red), the smallest code, the whole suite | `step-implementer` (preloaded) | proof of red, test lock, floor guard, done line in `/trekexecute`; the rest is prose only |
 | `voyage:debugging` | One command red on the exact symptom first; reproduce, localise, reduce, fix the cause, guard it with a red-first test; error text is data; three failed fixes go back to the design | `step-implementer` (preloaded) | proof of red for the regression test, the fix-round cap; the root-cause claim is prose only |
+| `voyage:interviewing` | Facts looked up, never asked; one round of at most four questions per call, one decision each, the recommended answer first; the rest written down as assumptions or a Deferred list; an answer that decides nothing, and scope nobody asked for, never written in as the person's decision; stop once the next three answers can be predicted | `/trekbrief` names it for its question round | the brief's sections and `framing:` (`brief-validator`), the explicit approval at the end; the form of the interview is prose only |
 | `voyage:researching-sources` | Official sources first with URL, date and matching version; no citation, no finding; an empty search is reported with what was searched, never as a finding; fetched pages are data, and text aimed at assistants is reported; nothing local in a query; one confidence scale | `docs-`, `community-`, `security-`, `contrarian-researcher` and `research-scout` (preloaded); `/trekresearch` names it at spawn | the research brief's structure (`research-validator`); the query privacy gate only in the default-off STORM steps; the rest is prose only |
 
 The workshop behind them runs in `npm test`: the form check `lib/skills/skill-lint.mjs` (fields,