docs: improve OpenWebUI integration guide

[rlippmann]

Summary

Improves the OpenWebUI reference integration README so it reads more like user-facing supporting documentation and less like an internal test plan.

Changes include:

• renaming the behavior overview to Core behavior
• renaming runtime checks to Verify behavior
• making trace output the primary verification path
• keeping forwarded-request inspection as an optional advanced check
• simplifying the base pipe and directive-drafter verification guidance
• clarifying setup and configuration wording

Why

The OpenWebUI integration README may be used as supporting material by OpenWebUI users. The previous version was technically accurate, but too checklist-oriented and engineering-focused.

This update keeps the same documented behavior while making the guide easier to skim and follow.

Example metadata

• Enforcement point: prompt construction / checkpoint continuation
• Domain: OpenWebUI chat integration
• Technology/runtime: Open WebUI
• Example type: reference integration
• Does this use directive drafter? yes, optional variant only
• 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

Documentation-only change. No pipe behavior, tests, dependencies, or runtime logic changed.