FU-P13-T16: Document multi-agent MCP usage and single Web UI host

[SoundBlaster]

Description

This PR delivers FU-P13-T16 (documentation-only) and clarifies multi-agent MCP behavior:

• documents Web UI ownership semantics (single listener per host:port)
• explains why MCP tools can remain healthy while dashboard hosting is unavailable
• adds broker-mode multi-agent topology guidance and Zed --broker-connect example
• adds troubleshooting flow for "tools green, dashboard unreachable"

Updated files:

• README.md
• docs/broker-mode.md
• docs/webui-setup.md
• docs/troubleshooting.md
• workplan/archive artifacts for FLOW (SPECS/Workplan.md, SPECS/INPROGRESS/next.md, SPECS/ARCHIVE/...)

Validation commands run:

• PYTHONPATH=src pytest (672 passed, 5 skipped)
• ruff check src/
• mypy src/
• PYTHONPATH=src pytest --cov=src/mcpbridge_wrapper --cov-report=term-missing (91.5%)

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactoring
• CI/CD improvement

Quality Gates

Before submitting, ensure all quality gates pass:

make check

Or run individually:

• make test - All tests pass with ≥90% coverage
• make lint - No linting errors
• make format - Code is properly formatted
• make typecheck - Type checking passes
• make doccheck - Documentation is synced with DocC (if docs changed)

Documentation Sync

If you modified files in docs/, ensure corresponding DocC files are also updated:

docs/ file	DocC file
docs/installation.md	mcpbridge-wrapper.docc/Installation.md
docs/cursor-setup.md	mcpbridge-wrapper.docc/CursorSetup.md
docs/claude-setup.md	mcpbridge-wrapper.docc/ClaudeCodeSetup.md
docs/codex-setup.md	mcpbridge-wrapper.docc/CodexCLISetup.md
docs/troubleshooting.md	mcpbridge-wrapper.docc/Troubleshooting.md
docs/architecture.md	mcpbridge-wrapper.docc/Architecture.md
docs/environment-variables.md	mcpbridge-wrapper.docc/EnvironmentVariables.md
README.md	mcpbridge-wrapper.docc/mcpbridge-wrapper.md

• Documentation changes are synced with DocC catalog (or N/A)

Testing

• Added/updated tests for new functionality
• All tests pass locally
• Manually tested the changes

Checklist

• Code follows the project's style guidelines
• Self-review completed
• Comments added for complex code
• Documentation updated (if needed)
• No new warnings generated
• PR title is descriptive