plan-*-review: shared GSTACK REVIEW REPORT rewrite deletes earlier review's summary; AUQ option label easy to omit #3219

Two issues seen running /plan-design-review then /plan-eng-review on the same plan file (gstack 1.91.101.0).

1. Report rewrite deletes another review's completion summary. plan-design-review writes its Completion Summary box inside the ## GSTACK REVIEW REPORT section. plan-eng-review's "Write to the plan file" step deletes that whole section (heading to next ## or EOF) and appends a fresh report, so the design review's per-pass scores, decision count and deferrals disappear from the file; only its one-line table row survives.

Suggestion: have each plan-*-review write its completion summary as its own ## <Review> completion summary section above the terminal report, and document that everything under ## GSTACK REVIEW REPORT is regenerated by the next review.

2. AskUserQuestion option label easy to drop. The decision-brief format describes options in prose (label, description, (recommended) on the label). In a 7-pass review the model repeatedly wrote the long description and omitted the short label field, causing InputValidationError round trips. Suggestion: show the per-option shape as explicit fields (label: short, description: long) in the Format section and add "every option has both label and description; (recommended) goes on the label" to the pre-emit self-check.