fix: delete AskUserQuestion fallback (root cause of forever war)

The /plan-eng-review skill failed to fire AskUserQuestion on a real
plan review and surfaced 4 calibration decisions via prose instead.
Investigation traced this to a "fallback when neither variant is
callable" clause in the preamble that the model rationalizes around
as a general escape hatch from "fanning out round-trip AUQs," even
when an AUQ variant IS callable. Codex review confirmed the fallback
exists in 8 inline sites with 2 surviving escape hatches the original
narrowing missed (a "genuinely trivial" exception duplicated across
all 4 plan-* templates, and a "outside plan mode, output as prose
and stop" branch in the preamble itself).

Net deletion in skill text. Closes both branches of the deleted
fallback (plan-file write AND prose-and-stop) and the trivial-fix
exception with a single hard rule:

  If no AskUserQuestion variant appears in your tool list, this
  skill is BLOCKED. Stop, report `BLOCKED — AskUserQuestion
  unavailable`, and wait for the user.

Honest about being a model directive, not a runtime guard — none of
the PTY harness helpers enforce BLOCKED today. The architectural
improvement is that the model has fewer alternatives to obey it
against. Runtime enforcement is a follow-up TODO.

Sources changed:
- scripts/resolvers/preamble/generate-ask-user-format.ts: delete both
  fallback branches; replace with 1-line BLOCKED rule
- scripts/resolvers/preamble/generate-completion-status.ts: delete
  fallback in generatePlanModeInfo
- plan-eng-review/SKILL.md.tmpl: delete fallback at Step 0 + Sections
  1-4 (5 instances) + delete trivial-fix exception
- office-hours/SKILL.md.tmpl: delete fallback in approach-selection
- plan-ceo-review/SKILL.md.tmpl: delete trivial-fix exception
- plan-design-review/SKILL.md.tmpl: delete trivial-fix exception
- plan-devex-review/SKILL.md.tmpl: delete trivial-fix exception

Generated SKILL.md regen lands in a follow-up commit per the bisect
convention (template changes separate from regenerated output).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plan-devex-review/SKILL.md.tmpl

@@ -669,11 +669,10 @@ DX reviews:
 * **Map to DX First Principles above.** One sentence connecting your recommendation
   to a specific principle (e.g., "This violates 'zero friction at T0' because
   [persona] needs 3 extra config steps before their first API call").
-* **Escape hatch (tightened):** If a section has zero findings, state "No issues,
-  moving on" and proceed. If it has findings, use AskUserQuestion for each — a
-  gap with an "obvious fix" is still a gap and still needs user approval before
-  any change lands in the plan. Only skip AskUserQuestion when the fix is
-  genuinely trivial AND there are no meaningful DX alternatives. When in doubt, ask.
+* **Zero findings:** if a section has zero findings, state "No issues, moving on"
+  and proceed. Otherwise, use AskUserQuestion for each gap — a gap with an
+  "obvious fix" is still a gap and still needs user approval before any change
+  lands in the plan.
 * Assume the user hasn't looked at this window in 20 minutes. Re-ground every question.
 
 ## Required Outputs