Add oh-my-pi (omp) as a supported coding agent

[zhulinchng]

What

ucode can now configure, launch, validate, and register MCP servers for oh-my-pi (omp, @oh-my-pi/pi-coding-agent), alongside the existing pi entry. ucode configure --tools omp, ucode omp, ucode doctor, ucode status, and ucode revert all cover it.

How

• New agents/omp.py (mirrors pi.py, no shared abstraction): isolated ~/.ucode/omp-home/.omp/agent, YAML models.yml with the three Databricks providers (anthropic-messages / openai-responses / google-generative-ai), default model pinned via modelRoles.default in config.yml (models.yml root must be providers-only per omp's schema), baked-token refresh thread, --print validation, {command, args}-only MCP entries (omp's stdioServer forbids other keys).
• Registry, discovery, launch, state, and MCP wiring; base_urls["omp"]; MCP backup restore on revert. No OAUTH_TOKEN (omp never reads it).
• pyyaml promoted to a direct dependency (2-line lock delta).

flowchart LR
    C[ucode configure --tools omp] --> W[agents/omp.write_tool_config]
    W --> M[models.yml: providers + apiKey]
    W --> D[config.yml: modelRoles.default]
    L[ucode omp] --> R[token refresh thread]
    R --> O[omp binary\nPI_CODING_AGENT_DIR=omp-home]
    O --> G[AI Gateway\nanthropic/codex/gemini]
    P[ucode configure mcp] --> J[omp-home mcp.json\nucode mcp-proxy stdio]

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Verification

• ruff check + ruff format --check clean; full unit suite 2344 passed.
• Live probe against omp 18.1.13 with a localhost capture server: omp models resolves the catalog; --print routes POST /anthropic/v1/messages?beta=true with bearer auth and no eager_input_streaming; the codex path hits /codex/v1/responses with the ucode UA.

Non-goals

Managed-config support (server proto has no omp variant), OSS models, e2e additions.