Add workflow fixture tests for skill contracts

[Dimon94]

Parent

#40

What to build

Add minimal workflow fixtures to the existing Jest test suite so contract behavior is tested as process, not just as scattered prose strings. The fixtures should prove the serial workflow, parallel environment shape, quality gate path, and authoring gate shape at the smallest useful seam.

This slice must not introduce a new test framework, real child threads, real PR automation, or large golden snapshots.

Acceptance criteria

• A serial fixture covers task contract handoff through execution selection, verification verdict shape, and closeout input.
• A parallel fixture covers Execution Environments, child dispatch boundary, and integration gate fields.
• A quality fixture covers review finding, Failure Ledger candidate, verification classification, and closeout/postmortem trigger input.
• An authoring fixture covers skill frontmatter, reads wiring, no user trigger for Chain Skills, and completion criterion presence where applicable.
• Tests run in the existing Jest suite without new framework scaffolding.
• Fixtures avoid broad snapshots and real external services.

Blocked by

• Add task-contract Chain Skill #42
• Add workflow-chain-contract Chain Skill #43
• Add quality-gate-contract Chain Skill #44
• Add execution-environment-contract Chain Skill #45