Support parent execution_id for composed side effects

[azender1]

Problem

Some workflows compose multiple side effects across boundaries, for example:

• payment
• database write
• notification

Each side-effect boundary should own its own execution guard, but retries still need a shared correlation mechanism.

Proposal

Add support for a parent execution_id or correlation ID so:

• each boundary keeps separate execution ownership
• composed workflows still converge safely under retries
• tooling can inspect related execution records together

Why this matters

This allows Execution Guard to support:

• cross-tool retries
• payment + DB write workflows
• multi-step agent actions
• partial failure recovery