[Phase 2] Validate the folded feature-ideation enhancement mode on real .github-private Discussions (next ring) #875

Story

As a maintainer making the next-ring go/no-go decision,
I want exercise the folded enhancement mode on .github-private's existing un-enhanced Ideas Discussions with dry-run then live, and confirm the idempotent single-comment behavior before any deprecation or promotion,
so that we prove the unified capability actually works on real ideas — no synthetic fixtures — so the deprecation cutover and the first ring promotion are safe.

Acceptance Criteria

1. A dry-run of .github/workflows/feature-ideation.yml (workflow_dispatch with dry_run=true) against the next ring logs the intended enhancement for an existing un-enhanced human Idea (candidate: Enhanced Prompting Frameworks #851 'Enhanced Prompting Frameworks') to the artifact without posting.
2. A subsequent live run posts exactly ONE structured enhancement comment (sharpened problem / context / impact-effort / acceptance criteria) on that Idea and writes the idempotency marker.
3. A second live run on the same Idea is a no-op (the marker prevents re-enhancement).
4. A bot-authored Ideas Discussion is skipped (the category.slug=='ideas' && user.type!='Bot' guard holds).
5. The dry-run artifact and the run links are recorded as a go/no-go note on this issue. (Ring promotion past next is itself a cross-repo, central channel-tag move on petry-projects/.github — an untracked prerequisite, not an action of this story; this story only records the go/no-go signal that gates it.)

Tasks / Subtasks

• Run feature-ideation.yml via workflow_dispatch with dry_run=true and capture the intended-enhancement artifact for Enhanced Prompting Frameworks #851. (AC: test issue from agent #1)
• Run it live and verify exactly one structured comment plus the idempotency marker on Enhanced Prompting Frameworks #851. (AC: Go-live improvements for PR review agent #2)
• Re-run live and confirm a no-op; separately confirm a bot-authored idea is skipped. (AC: Add @claude delegation, auto-merge, and rebase handling #3, Optimize review: small-PR and incremental fast paths #4)
• Write the go/no-go validation note (artifact + run links) on this issue. (AC: feat: add Copilot engine support via REVIEW_ENGINE toggle #5)

Dev Notes

• This is a hands-off human validation/operations gate (go/no-go on live agent behavior against real Discussions), not a code change — hence hands_off. It must run AFTER story 2 (the .github-private stub is pinned to feature-ideation/next) and AFTER the folded enhancement mode is live on that channel (untracked prerequisite in petry-projects/.github).
• Validation candidates (open + human-authored + un-enhanced as of 2026-06-21, per Initiative: unify Discussion-triggered ideation into a feature-ideation mode, deprecate idea-enhancer, and roll out fleet-wide via canary rings #866): .github-private Enhanced Prompting Frameworks #851. Use real Discussions only — no synthetic fixtures.
• The idempotency marker to look for is <!-- idea-enhancer:enhanced --> (the existing marker; the folded mode must reuse it for cross-cutover continuity — see the marker-continuity prerequisite). If the folded mode posts but the marker differs, that is a FAIL — flag it, do not proceed.
• Note: while idea-enhancer.yml is still present (until story 4), .github-private may transiently show TWO comments on a brand-new idea (one per enhancer). That is expected in the next/dogfood ring; this story validates the FOLDED mode's own single-comment correctness on Enhanced Prompting Frameworks #851. The 'exactly one after cutover' check belongs to story 4.
• Trigger surface: feature-ideation.yml exposes a dry_run workflow_dispatch input that logs intended Discussion mutations to a JSONL artifact; the discussion:created path enhances a single targeted idea via target_discussion.

Project Structure Notes

No repo files change; this is an operational validation of the workflow against live Discussions, recorded as an issue note.

References

• .github/workflows/feature-ideation.yml#dry_run
• .github/workflows/feature-ideation.yml#discussion-created-guard
• discussion Initiative: unify Discussion-triggered ideation into a feature-ideation mode, deprecate idea-enhancer, and roll out fleet-wide via canary rings #866 (validation candidates per ring)

Likely target surface

• .github/workflows/feature-ideation.yml (executed, not edited)

Story prepared by the BMAD Scrum Master (Bob) for epic #872. Status: ready-for-dev.