[plan] Split `frontmatter_types.go` into types and parsing files

[github-actions]

Objective

Split pkg/workflow/frontmatter_types.go (957 lines) by separating type definitions from parsing logic.

Context

Discussion: #26221

This file contains both type definitions and parsing logic. Per AGENTS.md conventions, parsing functions should live in a separate file when the combination exceeds the threshold.

Approach

1. Keep all type and struct declarations in frontmatter_types.go (target ≤ 300 lines)
2. Move ParseFrontmatterConfig, parseRuntimesConfig, parsePermissionsConfig, and other parse functions to a new frontmatter_parsing.go file

Files to Modify

• Split: pkg/workflow/frontmatter_types.go
• Create: pkg/workflow/frontmatter_parsing.go

Acceptance Criteria

• frontmatter_types.go contains only type/struct declarations and is ≤ 300 lines
• New frontmatter_parsing.go is ≤ 300 lines
• make build && make test-unit pass without errors
• make fmt && make lint pass without errors

Generated by Plan Command for issue #discussion #26221 · ● 150.1K · ◷

• expires on Apr 16, 2026, 5:18 PM UTC

[github-actions]

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