chore(ship): prompt for PR evidence in the ship skill

[chaliy]

What changed

The /ship command's Push-and-PR phase now prompts for evidence in the PR body — a Before / After with proof: CLI/API output or logs (fetch results, MCP responses). The Body line is also updated to reference .github/pull_request_template.md with the current sections (What changed / Why / Before / After / Risk / Checklist) and to center the description on functional change and impact.

Why

The ship flow already gathers validation, but the command didn't tell the agent to attach that proof to the PR, and its body reference still listed the old What/Why/How sections. Reviewers benefit from seeing the change work, not reading that it does.

Before / After

Docs/skill-guidance only — no runtime behavior changes.

• Before: Body step said "use What / Why / How / Risk / Checklist."
• After: references the PR template (What changed / Why / Before / After / Risk / Checklist) + functional framing, and adds an Evidence line (CLI/API output or logs), noting when there's no observable change.

Risk

• Low
• Skill/docs only; no source, config, or CI logic touched.

Checklist

• Unit tests are passed — N/A (skill/docs only)
• Smoke tests are passed — N/A
• Documentation is updated
• Specs are up to date and not in conflict

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