Add live action-boundary metrics workflow

[safal207]

Goal

Add a live CI workflow that runs the guarded-action demo path and emits action-boundary metrics from the generated audit log.

Why

The fixture baseline is now in place. The next evidence layer is a live run:

start demo upstream
start ProofPath gateway
run no-approval guarded action
run approved guarded action
parse generated audit JSONL
emit metrics JSON
upload artifacts

Scope

• Add a GitHub Actions workflow for the live action-boundary demo.
• Use scripts/collect_action_boundary_metrics.py to parse the generated audit log.
• Upload audit log, metrics JSON, and service logs as workflow artifacts.
• Keep claim bounded: this is a CI demo run, not production benchmark coverage.

Acceptance criteria

• Workflow starts upstream and gateway locally.
• Workflow runs both demo requests.
• Workflow generates an audit JSONL file.
• Workflow emits action-boundary metrics JSON.
• Workflow verifies the expected fixture-level counts.
• Rust CI remains green.

Reviewer phrase

The live action-boundary workflow turns the fixture baseline into a reproducible CI demo run with generated audit and metrics artifacts.