feat: auto-scaled adversarial review by diff size

Replace config-driven Codex review step with automatic adversarial review
that scales by diff size: small (<50 lines) skips adversarial, medium
(50-199) gets cross-model adversarial, large (200+) gets all 4 passes.

Adds Claude adversarial subagent as fallback when Codex unavailable.
Review log uses new "adversarial-review" skill name with source/tier fields.
Dashboard updated to read both adversarial-review and legacy codex-review.

ship/SKILL.md.tmpl

@@ -11,6 +11,7 @@ allowed-tools:
   - Edit
   - Grep
   - Glob
+  - Agent
   - AskUserQuestion
   - WebSearch
 ---
@@ -403,7 +404,7 @@ For each classified comment:
 
 ---
 
-{{CODEX_REVIEW_STEP}}
+{{ADVERSARIAL_STEP}}
 
 ## Step 4: Version bump (auto-decide)
 
@@ -644,7 +645,7 @@ doc updates — the user runs `/ship` and documentation stays current without a
 - **Never skip tests.** If tests fail, stop.
 - **Never skip the pre-landing review.** If checklist.md is unreadable, stop.
 - **Never force push.** Use regular `git push` only.
-- **Never ask for trivial confirmations** (e.g., "ready to push?", "create PR?"). DO stop for: version bumps (MINOR/MAJOR), pre-landing review findings (ASK items), Codex critical findings ([P1]), and the one-time Codex adoption prompt.
+- **Never ask for trivial confirmations** (e.g., "ready to push?", "create PR?"). DO stop for: version bumps (MINOR/MAJOR), pre-landing review findings (ASK items), and Codex structured review [P1] findings (large diffs only).
 - **Always use the 4-digit version format** from the VERSION file.
 - **Date format in CHANGELOG:** `YYYY-MM-DD`
 - **Split commits for bisectability** — each commit = one logical change.