docs: update Python examples for dev13 APIs

[rlippmann]

Summary

Update Python example and reference integration documentation for:

• context-compiler>=0.9.0dev13
• context-compiler-directive-drafter>=0.2.0dev2

Why

Keep the Python examples and reference integrations aligned with the current Context Compiler contract after the dev13/dev2 upgrade.

This documents the current ownership boundary:

• Drafter produces candidate directives.
• Hosts control workflow and submission.
• Core remains authoritative for validation and state transitions.

Example metadata

• Enforcement point: existing Python reference integrations and examples
• Domain: multiple example domains
• Technology/runtime: Python
• Example type: repository maintenance
• Does this use directive drafter? should normally be no: No new usage added; existing drafter documentation updated where applicable.
• 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

Updated:

• Python dependency references.
• Engine() and decision-object documentation.
• Replacement semantics:
  • source policy must exist;
  • missing source returns REPLACEMENT_SOURCE_MISSING;
  • repairs are advisory.
• LiteLLM and Open WebUI reference integration documentation.

Validation:

• npx --yes markdownlint-cli2
• ./scripts/validate_python.sh
• git diff --check

All passed.