Remove obsolete safe-jobs backwards compatibility references

[Copilot]

The old top-level safe-jobs: syntax is already rejected by JSON schema validation, but comments incorrectly claimed backwards compatibility existed. No code actually reads from the old location.

Changes

• pkg/workflow/compiler.go: Removed claim of "old location (safe-jobs) for backwards compatibility"
• pkg/workflow/safe_jobs.go: Clarified parseSafeJobsConfig() and extractSafeJobsFromFrontmatter() are internal helpers that never read user's top-level safe-jobs: key
• pkg/workflow/safe_jobs_test.go: Added context that tests validate internal parsing, not user frontmatter
• pkg/workflow/safe_jobs_syntax_test.go: Added explicit tests verifying schema rejection of old syntax

Current Behavior

Old syntax is rejected with helpful error:

# ❌ Rejected by schema
safe-jobs:
  deploy:
    runs-on: ubuntu-latest

# Error: Unknown property: safe-jobs. Did you mean: safe-outputs

New syntax compiles correctly:

# ✅ Accepted
safe-outputs:
  jobs:
    deploy:
      runs-on: ubuntu-latest

All 74 repository workflows continue to compile successfully.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[task] Add deprecation warning for safe-jobs legacy syntax</issue_title>
<issue_description>## Objective
Add deprecation warning when the old safe-jobs syntax is detected, guiding users to migrate to the new safe-outputs.jobs location.

Context

Migration to safe-outputs is 100% complete (0/74 workflows use old syntax), but backwards compatibility code still silently supports the old location. Users should be notified when using deprecated syntax.

Related to #3511

Approach

1. Detect when workflow uses old safe-jobs: location
2. Emit warning message to stderr using console.FormatWarningMessage()
3. Continue processing (maintain backwards compatibility)
4. Include migration guidance in warning message

Files to Modify

• Update: pkg/workflow/safe_jobs.go
  • Add deprecation check in parseSafeJobsConfig() function
  • Emit warning when old syntax detected
• Update: pkg/workflow/compiler.go
  • Add warning when both old and new syntax detected
• Update: Documentation
  • Add migration guide to troubleshooting section
  • Update examples to show recommended syntax

Warning Message Format

Warning: 'safe-jobs' configuration is deprecated and will be removed in v2.0.0
Please migrate to 'safe-outputs' syntax. See migration guide: [URL]

Acceptance Criteria

• Warning emitted when safe-jobs: detected in frontmatter
• Warning includes clear migration instructions
• Warning references documentation URL for migration guide
• Backwards compatibility maintained (no breaking changes)
• Test case added for deprecation warning
• Documentation updated with migration guide
• Consider adding migration timeline (removal in next major version)
  Related to [Schema Consistency] 🔍 Schema Consistency Check - November 9, 2025 #3511

AI generated by Plan Command for discussion #3511</issue_description>

Comments on the Issue (you are @copilot in this section)

@pelikhan @copilot remove old syntax supper entirely

• Fixes [task] Add deprecation warning for safe-jobs legacy syntax #3518

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[Copilot]

Pull Request Overview

This PR updates documentation and comments to clarify that the old top-level safe-jobs syntax is no longer supported, and users must use the new safe-outputs.jobs syntax instead. The schema validation already enforces this restriction since the main workflow schema has "additionalProperties": false and does not include safe-jobs as a valid property.

Key Changes:

• Added comprehensive tests to verify the old safe-jobs syntax is rejected and the new safe-outputs.jobs syntax works correctly
• Updated comments throughout the codebase to explicitly document that parseSafeJobsConfig is an internal helper and that user workflows must use safe-outputs.jobs

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
pkg/workflow/safe_jobs_test.go	Updated comment to clarify that the test validates internal parsing logic, not user-facing syntax
pkg/workflow/safe_jobs_syntax_test.go	Added new test file with two tests: one verifying old syntax rejection and one verifying new syntax acceptance
pkg/workflow/safe_jobs.go	Enhanced comments on parseSafeJobsConfig and extractSafeJobsFromFrontmatter to explicitly state that top-level safe-jobs is not supported
pkg/workflow/compiler.go	Updated comment to remove backward compatibility reference and clarify only safe-outputs.jobs location is checked

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