[plan] Add multi-repository pattern library to developer.instructions

[github-actions]

Objective

Document common multi-repository automation patterns to proactively guide users building cross-repo workflows.

Context

From discussion #12461: Only 1/8 workflows (PM-1) mentioned multi-repo scenarios. Many organizations need automation across multiple repositories (monorepo, microservices, shared libraries).

Approach

1. Add a new section to .github/instructions/developer.instructions.md: "Multi-Repository Patterns"

2. Document 3 common patterns:

   • Monorepo pattern: Single workflow, multiple project paths
   • Microservices pattern: Coordinated workflows across services
   • Shared library pattern: Central repo triggering dependent repo workflows

3. For each pattern, provide:

   • Use case description
   • Repository structure example
   • Workflow configuration snippet
   • GitHub MCP queries for cross-repo data

4. Add guidance for when to suggest multi-repo patterns:

   • DevOps workflows (deployment, monitoring)
   • PM workflows (release notes, feature digest)
   • QA workflows (integration testing across services)

Files to Modify

• Update: .github/instructions/developer.instructions.md
  • Add "Multi-Repository Patterns" section
  • Include 3 pattern examples with code snippets
  • Add proactive suggestion guidance

Acceptance Criteria

• Section documents all 3 patterns with code examples
• Each pattern includes repository structure diagram (text-based)
• GitHub MCP query examples for cross-repo operations
• Clear guidance on when to suggest each pattern
• Links to relevant GitHub documentation (repository_dispatch, workflow_run events)

AI generated by Plan Command for discussion #12461

[github-actions]

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