Integration: Strict Environment Supremacy Validation

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### Description
Establish the "Strict Environment Supremacy" integration test suite. This slice explicitly tests the full top-level RolloutStateMachine to guarantee that runtime hot-reloads correctly respect the existing configuration merge hierarchy (Local -> Remote -> Env). Construct a specific integration scenario: Configure a local setting (bla = a), an initial remote setting (bla = b), and an environment variable (bla = c). Trigger a hot-reload with a new remote configuration (bla = d). Verify that the final merged configuration delivered to the application still strictly resolves bla = c.

### Acceptance criteria
- [ ] A top-level integration test is implemented simulating the Local -> Remote -> Env hierarchy.

- [ ] Hot-reloading a remote value that conflicts with a local environment variable correctly discards the remote value in favor of the environment variable.

### Blocked by
Issue #125

User stories covered: 7

This issue targets the top-level RolloutStateMachine; first resolve or review blocked issue #125, then locate the existing integration-test entry point. Add the Local → Remote → Env scenario, trigger the remote hot-reload, and verify that the delivered configuration keeps bla = c.

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