Add per-model descriptions + repo-cleanup polish

- models.yaml: add 'description' field for all 5 models (generic, anyone-can-use)
- ModelDef gains optional description: str | None field
- UI: render description below meta tags; mute the repo line further
- escapeHtml() for safety in case descriptions/names contain HTML chars
- Update runbook: how to add a new model with description

image/app/models.py

@@ -12,6 +12,7 @@ class ModelDef(BaseModel):
     capabilities: list[str] = Field(default_factory=list)
     expected_ready_seconds: int = 300
     vllm_args: list[str] = Field(default_factory=list)
+    description: str | None = None
 
 
 class Defaults(BaseModel):