docs(filter): document cross-stack DNS gotcha for ORCHESTRATOR_URL

[Yambr]

Summary

• Adds a Troubleshooting entry to docs/openwebui-filter.md covering the case where docker-compose.yml and docker-compose.webui.yml end up on separate Docker networks because their Compose project names diverge, so the filter cannot resolve computer-use-server and the preview/system-prompt path silently degrades.
• Lists three remediation paths: shared project name (the intended setup), host.docker.internal env override, or hard-setting the ORCHESTRATOR_URL Valve in OWUI admin.
• Notes that the same root cause also affects the matching Tool Valve and the fix_large_tool_results env var.

Context

Reported in #94. The user followed the docs (docker-compose.webui.yml, filter v4.1.0) but the inline iframe never appeared and /system-prompt injection silently failed. Root cause was that the two compose stacks did not share a project name, so computer-use-server did not resolve from inside the OWUI container. They worked around it by setting the Valve to a host IP — fine, but the failure mode wasn't documented.

Test plan

• Render docs/openwebui-filter.md on GitHub and confirm the new "Filter cannot reach computer-use-server (cross-stack DNS)" section appears between "Preview opens in a new tab…" and "Non-http scheme…".
• No code changes, no test suite impact.

Closes #94.

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Generated by Claude Code

Summary by CodeRabbit

• Documentation
  • Expanded troubleshooting section with new guidance for resolving DNS connectivity issues between Open WebUI and the Computer Use Server. Includes symptom identification, root cause explanation, and three practical recovery options.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 47bba87b-6266-41bf-ac59-2c1da9412d3f

📥 Commits

Reviewing files that changed from the base of the PR and between d29621e and b3d6ea5.

📒 Files selected for processing (1)

• docs/openwebui-filter.md

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📝 Walkthrough

Walkthrough

This PR adds a troubleshooting section to the Open WebUI filter documentation that explains cross-stack DNS connectivity failures between Open WebUI and Computer Use Server, including symptoms, root cause (Docker Compose project name mismatches), and three recovery methods.

Changes

Cross-Stack DNS Troubleshooting Documentation

Layer / File(s)	Summary
Troubleshooting Guidance docs/openwebui-filter.md	New section (lines 106–119) documents symptoms of iframe preview failures in Docker Compose setups, attributes the root cause to network isolation from differing project names, and offers three solutions: restore shared project name, override ORCHESTRATOR_URL in environment variables, or hard-set the URL via OWUI admin panel Valve.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A DNS tangle was blocking the way,
Cross-stacks couldn't chat, oh what dismay!
But now troubleshooting shines so bright,
Three fixes to set the preview right,
Docker networks dance in the light! 🌐

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/compose-instructions-questions-PjNqK

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