feat(pipeline_step): Add emergency patch support for deployments

[fpacifici]

Summary

Adds support for emergency patches to the PipelineStep sentry-kube macro, allowing clients to override any deployment configuration without code changes.

Changes

• Add optional emergency_patch field to PipelineStepContext TypedDict
• Update parse_context() to handle emergency_patch parsing (supports both dict and YAML string)
• Apply emergency_patch as the final merge layer in run() method (after base + user + pipeline additions)
• Add comprehensive test verifying emergency patch overrides work correctly

Usage Example

{
    "service_name": "my-service",
    "pipeline_name": "profiles",
    "deployment_template": {...},
    "container_template": {...},
    "pipeline_config": {...},
    "pipeline_module": "sbc.profiles",
    "image_name": "my-image:latest",
    "segment_id": 0,
    "cpu_per_process": 1000,
    "memory_per_process": 512,
    # Optional: emergency patch to override any deployment settings
    "emergency_patch": {
        "spec": {
            "replicas": 3,
            "template": {
                "spec": {
                    "securityContext": {
                        "runAsNonRoot": True
                    }
                }
            }
        }
    }
}

Resolves STREAM-708

🤖 Generated with Claude Code

[linear]

STREAM-708 Support emergency patches on the consumer macro.

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

📋 Changelog Preview

This is how your changes will appear in the changelog.
Entries from this PR are highlighted with a left border (blockquote style).

---

New Features ✨

• (pipeline_step) Add emergency patch support for deployments by fpacifici in #233

• (sentry_integration) Exec app in subprocess by victoria-yining-huang in #217

Other

• Require sink at the end of a branch of the pipeline by fpacifici in #230
• Move gcssink config override out of the adapter by fpacifici in #228

---

_{🤖 This preview updates automatically when you update the PR.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}

[cursor]

Unremoved comments per reviewer request in PR discussion

Low Severity

The PR discussion shows reviewer @fpacifici requested "Please remove this comment" twice, but comments are still present in the test file. The inline comments like # Base template default, # Emergency patch to override replicas and add security context, and # Override base template in the test data appear to be what the reviewer wants removed.

Additional Locations (1)

• sentry_streams_k8s/tests/test_pipeline_step.py#L584-L585