[Bug]: multimodal-looker hangs when primary model is opencode/mimo-v2.5-free

[mocun33]

Bug Description

When multimodal-looker is configured with opencode/mimo-v2.5-free as its primary model, dispatching a look_at task causes the agent to hang indefinitely (zero response, no timeout error propagation).

Steps to Reproduce

1. Configure multimodal-looker in oh-my-openagent.json:

{
  "agents": {
    "multimodal-looker": {
      "model": "opencode/mimo-v2.5-free"
    }
  }
}

2. Dispatch a multimodal-looker task that reads an image.
3. Observe: the subagent hangs with no response.

Expected Behavior

Process the image and return analysis, or fail fast with a clear error.

Workaround

Use opencode/deepseek-v4-flash-free or opencode/big-pickle as primary instead — both work.

{
  "agents": {
    "multimodal-looker": {
      "model": "opencode/deepseek-v4-flash-free"
    }
  }
}

Root Cause

opencode/mimo-v2.5-free is not registered in omo plugin's known model list — the doctor flags it as (unknown). When the plugin hits an unknown model ID, it uses a compatibility fallback dispatch path that has a deadlock/infinite loop specific to this model.

Other opencode/ prefixed models (big-pickle, deepseek-v4-flash-free) don't trigger this hang because they go through a different dispatch path.

Additional Evidence

• multimodal-looker with opencode/deepseek-v4-flash-free + empty fallback chain → works (12s)
• multimodal-looker with opencode/big-pickle → works (15s)
• The read tool returns image data to multimodal-looker subagents but not to main orchestrator or other agent types (explore, general), confirming image routing is handled at the OpenCode API layer, not by the configured model.
• opencode/mimo-v2.5-free directly as primary → hangs
• opencode/mimo-v2.5-free reached via fallback chain → works

Doctor Output

Configured models rely on compatibility fallback
multimodal-looker=opencode/mimo-v2.5-free (unknown)

Suggestion

Add opencode/mimo-v2.5-free (and other common opencode/ prefixed free-tier models) to the known model registry in packages/model-core/ so they dispatch through the correct path instead of compatibility fallback.

Environment

• OS: Windows
• oh-my-openagent: latest