feat: --validate and --strict

[ChristopherHX]

Use act --validate --strict to test for errors of the strict schema without running anything.

Could report a small number of phantom problems, but this opt in variant should not make people defer updates.

Closes #2716

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ EDITORCONFIG	editorconfig-checker	9		0	0.04s
✅ REPOSITORY	gitleaks	yes		no	2.77s
✅ REPOSITORY	git_diff	yes		no	0.01s
✅ REPOSITORY	grype	yes		no	10.5s
✅ REPOSITORY	secretlint	yes		no	1.22s
✅ REPOSITORY	trivy-sbom	yes		no	0.39s
✅ REPOSITORY	trufflehog	yes		no	3.83s

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

[codecov]

Codecov Report

Attention: Patch coverage is 76.92308% with 6 lines in your changes missing coverage. Please review.

Project coverage is 74.56%. Comparing base (5a80a04) to head (02b539d).
Report is 197 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/root.go	50.00%	2 Missing and 1 partial ⚠️
pkg/model/workflow.go	87.50%	2 Missing ⚠️
pkg/model/planner.go	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2717       +/-   ##
===========================================
+ Coverage   61.56%   74.56%   +12.99%     
===========================================
  Files          53       72       +19     
  Lines        9002    11085     +2083     
===========================================
+ Hits         5542     8265     +2723     
+ Misses       3020     2188      -832     
- Partials      440      632      +192     

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