[instructions] Sync github-agentic-workflows.md with v0.42.2 documentation

[github-actions]

Instructions Update - Synchronized with v0.42.2

This PR updates the github-agentic-workflows.md instruction file based on documentation changes since v0.40.1.

Changes Made

Added secrets: field documentation (from #13717)

• Documents secret value configuration with GitHub Actions expressions
• Includes both string and object formats with descriptions
• Adds security best practices (never commit plaintext, use environment-specific secrets)

Added agent: field to engine configuration (from #13786)

• Documents custom agent file configuration for Copilot engine
• References .github/agents/{agent}.agent.md file structure
• Enables specialized agent behaviors for specific tasks

Added security warnings for custom execution contexts (from #13808)

• Added security notices to steps:, post-steps:, and jobs: fields
• Clarifies these contexts run OUTSIDE the firewall sandbox
• Warns against running agentic compute in deterministic contexts
• Emphasizes use only for data preparation, cleanup, and static analysis

Updated default toolsets clarification (from fc94389)

• Already applied: clarified users toolset excluded from defaults as GitHub Actions tokens don't support user operations

Documentation Commits Reviewed

• fc94389 - Fix build (toolsets clarification)
• 1f19af0 - Document firewall sandbox exclusion for custom steps, jobs, and hybrid workflows
• 1b9eecd - Document engine agent field for custom Copilot agent configuration
• 6b44ca6 - Add secrets field to workflow schema with validation

Validation

• Followed prompting best practices (imperative mood, minimal examples)
• Maintained technical tone and brevity
• Updated only necessary sections
• Verified accuracy against current documentation
• Removed no outdated content (none found)
• Added critical security warnings for firewall boundary crossing

AI generated by Instructions Janitor

• expires on Feb 7, 2026, 8:15 AM UTC

[github-actions]

🔍 PR Triage Results

Category: docs | Risk: low | Priority: 52/100

Scores Breakdown

• Impact: 25/50 - Critical instruction file updates including secrets field documentation and security warnings. Important for agent functionality.
• Urgency: 17/30 - Syncing instructions with latest docs (v0.42.2). Moderate urgency to maintain consistency.
• Quality: 10/20 - Good description, CI pending. Automated PR with validation checklist completed.

📋 Recommended Action: fast_track

Instructions updates should be fast-tracked to keep agent instructions synchronized with documentation. Low risk.

📦 Part of batch: batch-docs-001 (Documentation updates from automated workflows) with PRs #13874, #13873

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Triaged by PR Triage Agent on 2026-02-05

AI generated by PR Triage Agent