[task] Verify and document timeout-minutes default behavior

[github-actions]

Objective

Investigate the actual timeout-minutes default behavior and update schema documentation to match reality.

Context

The schema claims "Defaults to 15 minutes for agentic workflows" but no code implementation sets this default. This creates misleading documentation. Part of discussion #4010.

Current State

Schema location: pkg/parser/schemas/main_workflow_schema.json

Schema claim: "Defaults to 15 minutes for agentic workflows"

Implementation: Field is extracted but no default value is assigned:

TimeoutMinutes string // extracted from frontmatter, no default set

Investigation Steps

1. Search codebase for timeout-minutes default assignment
2. Check GitHub Actions default timeout (documented as 360 minutes / 6 hours)
3. Test actual workflow behavior when timeout-minutes is omitted
4. Determine intended behavior: 15 minutes or GitHub Actions default

Decision Required

Choose one of these paths:

Option A: Implement 15-minute default

• Add default value assignment in compiler
• Keep schema description as-is
• Files to modify: pkg/workflow/compiler.go or frontmatter extraction logic

Option B: Document actual behavior

• Update schema description to reflect GitHub Actions default (360 minutes)
• No code changes needed
• File to modify: pkg/parser/schemas/main_workflow_schema.json

Files to Investigate

• pkg/parser/schemas/main_workflow_schema.json - Schema documentation
• pkg/workflow/compiler.go - Compiler logic
• pkg/workflow/frontmatter_extraction.go - Field extraction
• Any engine-specific timeout handling

Acceptance Criteria

• Actual timeout-minutes default behavior is verified
• Schema documentation matches implementation
• If default is implemented, tests validate the 15-minute default
• If documentation is updated, it accurately reflects GitHub Actions behavior

Related Information

• GitHub Actions default timeout: 360 minutes (6 hours)
• Current schema claims 15 minutes but this may be unimplemented

AI generated by Plan Command for discussion #4010