Dogfood PatternKit in WorkflowFramework execution plumbing

[JerrettDavis]

Goal

Dogfood PatternKit in WorkflowFramework without blurring WorkflowFramework's own product boundary.

Candidate refactors

• Internal middleware/pipeline composition: evaluate PatternKit chain primitives for shared execution plumbing.
• Compensation/saga samples: evaluate PatternKit compensating transaction and saga primitives for examples or integration extensions.
• Scheduling/human task gates: review alignment with PatternKit timeout manager, scheduler-agent-supervisor, and manual task gate patterns.
• DI/hosting extensions: document where PatternKit.Hosting.Extensions can compose with WorkflowFramework hosting.

Acceptance criteria

• Keep WorkflowFramework's public workflow model intact.
• Use PatternKit for supporting implementation where it removes duplicated pattern plumbing.
• Add tests around ordering, short-circuiting, compensation, and cancellation behavior.

[JerrettDavis]

Implemented and merged in #29.