Warn against fully-qualified Closes owner/repo#N in PR bodies

[sebastientaggart]

GitHub's closing-keyword parser only populates closingIssuesReferences for the unqualified #N form. The fully-qualified Closes owner/repo#N form (even for same-repo refs) leaves that GraphQL edge empty, silently breaking native auto-close and downstream automation that reads the edge.

General harness guidance often nudges agents toward owner/repo#N as a universal cross-link format. This change adds explicit overrides in the two places that build PR bodies — /submit-for-review and /deploy — telling agents to use the unqualified form for closing keywords regardless of that general guidance.

Scope note: the original issue #80 described four gaps, but the other three (label-linked-issues.yml trigger, duplicate "Ready for Review" label scheme, missing close-on-qa-passed automation) do not apply to the current Code Cannon scaffolding — there is no such workflow in this repo, no duplicate label scheme, and closure is intentionally driven by /deploy's promotion PR rather than the qa-passed label (see docs/skills/deploy.md). The only real gap was the qualified-form footgun, which this PR fixes.

Issue #80

[sebastientaggart]

Review Summary

Verdict: APPROVE

Findings

No issues found. Code looks correct and follows project conventions.

The change adds a consistent Critical warning about using unqualified #N closing-keyword form across both source templates (skills/deploy.md, skills/submit-for-review.md) and all generated adapter outputs (claude, codex, cursor, gemini). Generated file hashes are updated accordingly, and the note is placed appropriately next to the existing closing-keyword guidance in each file. The PR description correctly scopes the fix relative to issue #80.