[Benchmark]: Measure governance request lifecycle

[rian-be]

Summary

Benchmark the governance request lifecycle so pending, approved, rejected, expired, and cancelled transitions stay visible over time.

Goal

Measure the overhead of request lifecycle transitions that govern how a mutation request moves through pending and terminal states.

Problem

Governance already models request lifecycle states and transitions, but that path is not benchmarked as a dedicated runtime surface.

Without a benchmark for request lifecycle behavior, changes in submission, transition handling, expiration, cancellation, or terminal state recording can quietly add overhead without being visible in runtime measurements.

Scope

• Benchmark submitting governance requests into pending state
• Benchmark transitioning requests through approval-related lifecycle states
• Benchmark expiring pending requests
• Benchmark cancelling pending requests
• Keep the benchmark focused on request lifecycle behavior rather than approval or execution internals
• Reuse existing governance benchmark helpers where they already exist
• Make scenario names explicit about the lifecycle transition being measured

Design Expectations

• The benchmark should measure real request lifecycle behavior rather than a toy loop.
• Pending and terminal transitions should remain visible where possible.
• Helper code should stay local to the benchmark project.
• Scenario names should make the lifecycle path obvious.

Suggested Measurements

• request submission to pending state
• request approval-related transition
• pending request expiration
• pending request cancellation

Acceptance Criteria

• Request lifecycle is benchmarked as a distinct governance scenario
• Pending transition cost is visible in the benchmark results
• Terminal lifecycle transition cost is visible in the benchmark results
• The benchmark remains centered on governance runtime behavior

Non-Goals

• This issue does not change governance runtime behavior
• This issue does not add provider-specific persistence benchmarks
• This issue does not optimize lifecycle transitions prematurely
• This issue does not add full integration or load testing

Notes

This issue is a child of the governance benchmark umbrella #73.