Warn and fail closed for sync ToolNode enforcement

[Muhammad-usman92]

Summary

• Warn during adrian.init() when WebSocket enforcement is enabled without a running event loop.
• Fail closed in sync ToolNode.invoke when policy state is not ready yet, or when BLOCK/HITL mode is active but no resolved verdict is available.
• Reuse existing blocked ToolMessage behaviour: [BLOCKED by security policy].
• Keep async ToolNode.ainvoke behaviour unchanged.

Test plan

• Added SDK regression coverage for sync ToolNode.invoke fail-closed enforcement.
• Added SDK coverage for the init warning when no running event loop exists.
• Ran focused SDK tests: 21 passed.
• Ran ruff on changed SDK files.

Checklist

• CLA signed (see CLA.md)
• Tests pass locally
• Docs updated where needed
• British English; no em-dashes; no marketing fluff