fix(core): harden runtime contract invariants

[AjayThorve]

Summary

• Ensures run_plan cleans up started runtimes on invoke errors and validates runtime handles before invoke/stop dispatch.
• Adds explicit unsupported capability routing instead of implying unimplemented Fabric-managed tools/skills/MCP execution.
• Adds doctor warnings for modeled-but-unimplemented service/http/native-plugin runtime surfaces and regenerates schema snapshots.
• Updates CodeRabbit config in the same concise style as NeMo Relay so reviews focus on public API/runtime correctness.

Test Plan

• cargo fmt --check
• git diff --check
• cargo test --workspace
• cargo check -p fabric-python
• python3 tests/smoke_cli.py
• python3 python/tests/smoke_native_sdk.py
• python3 python/tests/smoke_typed_config.py
• python3 python/tests/smoke_sdk.py

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Enterprise

Run ID: bfb70daf-3806-46af-bb84-c3ed682e6a32

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ajay/fabric-sdk-consumer-contract

---

_{Comment @coderabbitai help to get the list of available commands.}

[AjayThorve]

Superseded by #25 from AjayThorve:ajay/fabric-sdk-consumer-contract with DCO sign-off.