[Slack] Seed some rules

[kageiit]

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Summary by Gitar

• New Slack notifications category:
  • Created rules/slack/ with 4 automation rules for PR/MR lifecycle DM notifications
• Review request notifications:
  • pr-review-request.md sends Slack DMs to reviewers when assigned, with filtering for drafts/bots/self-reviews
• Review outcome notifications:
  • review-submitted-notification.md notifies authors of review verdicts (approved/changes/comments) with contextual emojis
• Merge readiness notifications:
  • ready-to-merge-notification.md alerts authors when all checks pass using platform-native mergeable_state checks
• Stale PR reminders:
  • stale-pr-reminder.md sends gentle DM nudges to reviewers after configurable waiting period (default: 3 days)

_{This will update automatically on new commits.}

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[gitar-bot-staging]

Code Review

Well-structured documentation PR that adds comprehensive Slack notification rules for PR lifecycle events. Clean and consistent format across all rule files.

What Works Well

• Comprehensive edge case handling: Each rule explicitly defines when NOT to apply (draft PRs, bot accounts, self-reviews), preventing notification spam and ensuring appropriate targeting
• Consistent documentation structure: All four rule files follow the same pattern with frontmatter, "When to Use This", "How It Works", "Examples", and "Why This Matters" sections, making them easy to understand and maintain
• Thoughtful error handling guidance: Each rule includes graceful failure scenarios (Slack user not found, API errors, rate limits) ensuring robust implementation
• Good platform awareness: Rules properly account for GitHub vs GitLab differences (e.g., mergeable_state vs merge_status, different bot detection patterns)
• Practical examples: Multiple examples per rule covering common scenarios and edge cases help implementers understand expected behavior

Rules ✅ All requirements met

Gitar Rules

✅ Rule Quality Standards: All 4 Slack rules have complete frontmatter and proper structure

_{5 rules not applicable. Show all rules by commenting gitar display:verbose.}

Options Auto-apply: off ✅ Code review

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Display: compact Hiding non-applicable rules.

Comment with these commands to change:

Auto-apply	✅ Code review	Compact
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