docs: enhance Copilot coding agent instructions with comprehensive repository context

[Copilot]

The existing .github/copilot-instructions.md was missing significant context present in CLAUDE.md, leaving the Copilot coding agent without key information about the codebase.

Added to copilot-instructions.md

• Build commands: run-hubagent, run-memberagent, staticcheck, fmt, vet
• E2E commands: e2e-tests-custom, collect-e2e-logs, custom cluster count (MEMBER_CLUSTER_COUNT)
• Docker/Images section: make push and individual docker-build-* targets
• Core API Types section: All major CRDs (CRP, RP, MemberCluster, ClusterResourceBinding, ResourceBinding, Work, snapshots)
• Key Controllers section: Each controller with its package path (Rollout, WorkGenerator, WorkApplier, Watcher controllers)
• Directory Structure section: Full layout including test/e2e/, test/integration/, test/scheduler/
• Watcher Pattern + Multi-API Version subsections under Code Conventions
• Test Coding Style section: Comment capitalization rules, struct comparison patterns (one-shot cmp.Diff, not field-by-field)

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• gh.io
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>✨ Set up Copilot instructions</issue_title>
<issue_description>Configure instructions for this repository as documented in Best practices for Copilot coding agent in your repository.

</issue_description>

Comments on the Issue (you are Copilot in this section)

• Fixes ✨ Set up Copilot instructions #537

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