docs(brainstorm-with-docs): уточнены границы артефактов по внешнему ревью

- Зачем:
  - внешнее ревью выявило риск двойной записи решений (spec/ADR) и
    терминологическую путаницу; правки документные, поведение не меняют.
- Что:
  - adr.md и spec.md: добавлен lifetime-критерий ADR vs spec (ADR — для
    решений, переживающих спеку; локальные остаются в спеке).
  - spec.md: разведены Options considered (до выбора) и Decisions (после).
  - SKILL.md: блок <validation> переименован в <self_review>, чтобы не
    путать с секцией ## Validation в spec.md.
  - README.md: честнее описано авто-срабатывание на Codex.
  - SKILL.md: у SEAM зафиксирован TODO(F1) про строку дивергенции
    (отложена ради чистого baseline на обкатке).
- Проверка:
  - python3 yaml-парс frontmatter; нет висячих ссылок на <validation>.

agents/.agents/skills/brainstorm-with-docs/SKILL.md

@@ -143,9 +143,16 @@ in [artifacts/context.md](artifacts/context.md) — don't batch them.
 
 ## 5. Synthesize options
 
-<!-- SEAM: v2 will prepend a divergence phase (idea-generation toolkit +
-     "at least one option the user didn't already imply") before this
-     convergence step. Keep this step self-contained so it can be split. -->
+<!-- SEAM / TODO(v2): prepend a divergence phase before this convergence step.
+     Full version = idea-generation toolkit (axis of variation, archetype
+     stances, inversion, steal-from-adjacent-domain, cost-shifting, pre-mortem,
+     constraint relaxation, null option).
+     TODO(F1): cheap pre-step — add one <core_rule>: "among the options, at least
+     one must be something the user did not already imply." Deliberately deferred
+     now to keep the v1 live-test baseline clean (we want to see how badly pure
+     convergence collapses into variations of one idea). Reconsider landing this
+     single line right after the first live test, before the full toolkit.
+     Keep this step self-contained so it can be split. -->
 
 Present 2-3 viable approaches. For each: short description, when it fits,
 benefits, trade-offs, risks, operational implications, documentation impact, and
@@ -178,7 +185,7 @@ Otherwise use the conventional homes — `CONTEXT.md` at the repo root, ADRs in
 `docs/runbooks/`). If the location isn't obvious, propose a path and confirm it
 as part of step 6 rather than guessing. Create directories lazily.
 
-Then go to `<validation>` and `<stop_condition>`.
+Then go to `<self_review>` and `<stop_condition>`.
 
 </how_to_do_it>
 
@@ -198,7 +205,10 @@ runbook. If it's a validation rule for this work → the spec.
 
 </shared_project_language>
 
-<validation>
+<self_review>
+
+This is a review of the document itself — distinct from a spec's `## Validation`
+section, which lists acceptance criteria for the implementation.
 
 Before presenting the final artifact, review it for: unclear terms, missing
 constraints, hidden assumptions, contradictions with existing docs, unnecessary
@@ -209,7 +219,7 @@ runbook, and context that does (or does not) belong in `CONTEXT.md`.
 If it's too large, propose splitting it. If it's too vague, continue the
 interview.
 
-</validation>
+</self_review>
 
 <stop_condition>