feat: migrate Python directive drafter integrations to dev4

[rlippmann]

Summary

Migrate the Python directive-drafter integrations and tests from dev2 expectations to context-compiler-directive-drafter==0.2.0dev4.

• Update exact project pins and regenerate uv.lock.
• Migrate runtime integrations from NoDirective to RejectedDirective and the dev4 fallback API.
• Migrate focused tests to dev4 reasons, sentinel behavior, and fallback rules.
• Update Open WebUI metadata and Python installation documentation.

Why

Keep the Python examples, reference integrations, tests, and installation metadata aligned with the published dev4 API while preserving Context Compiler as the authority over state.

Example metadata

• Enforcement point: Context Compiler state transitions and host integration boundaries
• Domain: multiple teaching examples
• Technology/runtime: Python, LiteLLM Proxy, Open WebUI Pipe
• Example type: reference integration / repository maintenance
• Does this use directive drafter? should normally be no: Yes, only in the explicitly drafter-focused integrations
• Does this derive state from model output? must be no for primary examples: No; drafted directives remain subject to host approval and Context Compiler processing

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 completed with ./scripts/validate_python.sh (212 passed, 6 skipped), Markdown lint (0 issues), and git diff --check.