[instructions] Sync github-agentic-workflows.md with v0.46.1

[github-actions]

Instructions Update - Synchronized with v0.46.1

This PR updates the github-agentic-workflows.md instructions file based on documentation and code changes since the last sync (v0.40.1).

Changes Made

• Breaking: Remove custom engine — The custom engine type was removed in v0.46.1. Updated engine field description, ID comment, validation enum, and added breaking change entry.
• Breaking: Remove copilot-sdk engine — The copilot-sdk engine was removed in v0.46.1. Added breaking change entry.
• New: runtimes.*.if conditional field — Runtime setup steps now support an optional if: GitHub Actions condition (e.g., "hashFiles('go.mod') != ''") to conditionally install runtimes based on file presence.
• New: assign-to-user.blocked field — Added blocked deny-list (supports exact matches and glob patterns like *[bot]) for the assign-to-user safe output.
• New: assign-to-user.unassign-first field — Added unassign-first option to clear existing assignees before assigning new ones.
• New: unassign-from-user.allowed and blocked fields — Added allowed and blocked filtering options to the unassign-from-user safe output.
• New: create-issue.group field — Added group: true option to automatically organize multiple issues as sub-issues under a parent.
• New: create-issue.close-older-issues field — Added close-older-issues option to close previous issues from the same workflow.
• Updated: expires field — Clarified that false can be used to explicitly disable expiration.
• Updated: roles: field — Corrected to on.roles: with deprecation note for top-level roles:.

Documentation Commits Reviewed

• ef87befc 📝 Update documentation across multiple files (📝 Update documentation across multiple files #16640)
• 24dcd694 Remove custom engine support (Remove custom engine support #16533)
• 293bb1b4 Remove copilot-sdk agent engine (Remove copilot-sdk agent engine #16519)
• 66682b91 Add unassign-first option to assign-to-user safe output (Add unassign-first option to assign-to-user safe output #16542)
• bdbe553f Add blocked deny list for assign-to-user and unassign-from-user (Add blocked deny list for assign-to-user and unassign-from-user safe outputs #16628)
• 41df3c37 Add conditional if expressions to runtime configuration (Add conditional if expressions to runtime configuration #16638)
• b5702725 Update safe outputs spec with discussions field (Update safe outputs spec with discussions field from PR #16509 #16516)

Validation

• Followed prompting best practices (imperative mood, minimal examples)
• Maintained technical tone and brevity
• Updated only necessary sections
• Verified accuracy against current codebase schema and documentation
• Removed outdated content (custom engine documentation)

AI generated by Instructions Janitor

• expires on Feb 21, 2026, 12:01 AM UTC