Migrate Python examples to Context Compiler 0.9 API

[rlippmann]

Summary

Migrates the Python example integrations to the Context Compiler 0.9 public API and updates the examples/tests to match the post-checkpoint architecture.

Why

The 0.9 API removed raw state access and continuation/checkpoint semantics. This branch updates examples to use the public engine boundary instead:

• engine.premise and engine.policies for semantic state access
• current Decision handling
• export_json() / import_json() for persistence where persistence is still part of the example
• directive drafter 0.2.0dev0 integration
• updated tests that previously asserted removed clarification/continuation behavior

Example metadata

• Enforcement point: multiple reference integration boundaries (LiteLLM proxy hooks, OpenWebUI integration, tool/authorization examples)
• Domain: reference integrations and repository migration
• Technology/runtime: Python examples, FastAPI, LiteLLM, OpenWebUI, directive drafter
• Example type: repository maintenance / reference integration
• Does this use directive drafter? should normally be no: Yes, only for examples that explicitly demonstrate drafter integration
• Does this derive state from model output? must be no for primary examples: No

Checklist

• Repository scaffolding / governance change
• One primary enforcement point
• Explicit authoritative state
• No model-derived state mutation
• Adversarial stub or equivalent test
• Observable runtime behavior change
• Domain vocabulary is natural
• Framework is secondary to the enforcement point
• Docs updated
• Tests/smoke checks added where practical

Notes

Validation:

• ./scripts/validate_python.sh
• 200 passed, 6 skipped (live tests)
• live integration tests verified after migration