Add task-preflight skill to stop zero-diff retry PRs on container-vuln and refactor tasks

[Copilot]

Container-vulnerability-fix and large-refactor tasks repeatedly burned full agent sessions: 5 of 6 closed PRs across three topics had 0 additions/0 deletions and no comments, so each retry restarted from zero with no record of the blocker.

Changes

• .github/skills/task-preflight/SKILL.md (new) — feasibility check that must pass before any code is pushed, covering the two topics that produce zero-diff PRs:

  • Container vulnerability tasks: reproduce with gh aw compile --force-refresh-container-pins --syft --grype --grant; unreachable image ⇒ blocker report. Otherwise route to one of the two real remediations — refresh the pin (commit changed .lock.yml) or add a scoped .grype.yaml ignore entry with a reason. Stale finding ⇒ report with scan output, no PR.
  • Large-refactor tasks: derive the offender list from make golint-custom (largefunc, 60-line default) instead of guessing, scope to a small named subset with a written extraction plan, keep it behaviour-preserving. Repo-wide rewrites like the 6096/6203-line attempt in #49825 are explicitly out.
  • Hard rules: never finish at 0/0 diff without explanation; never leave an empty placeholder PR; when blocked, emit a structured report (attempted / failure output / root cause / what unblocks it).

• AGENTS.md — one routing line in "Use these skills by intent", keeping the ambient file short per the repo's lazy-loading policy.

Blocker report shape the skill prescribes:

## Blocked: <tasktitle>**Attempted**: <commandsrun>
**Failure**: <exacterroroutput>
**Why it cannot proceed**: <rootcause>
**Unblocked by**: <access, upstream fix, scope decision needed from a maintainer>

Notes

The issue asks for a plan comment on the issue before opening a PR. No issue-comment tool was available in this environment, so the plan and links to the six prior closed PRs were published in the PR description before any content changes were pushed.

• Fixes[copilot-opt] Reduce zero-diff retry waste on container vulnerability & refactor tasks #53448

[github-actions]

PR Triage

Category: chore (WIP) | Risk: low | Priority: low (score 20)

• Draft, opened minutes ago with 0 diff — agent still generating changes (Fix zero-diff retries on container vulnerability and refactor tasks)
• Batch: pr-batch:wip-drafts (6 similar just-opened WIP PRs)

Recommended action: defer — recheck once agent finishes and diff is populated

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