Swap out the standard `MCPToolProgressManager` from fast-agent with
the local `EnrichedMCPToolProgressManager` from `pallas.progress` to
provide richer progress reporting during tool execution in the
multimodal MCP server.
Add optional `model` and `model_capabilities` fields to agent definitions
in agents.yaml, allowing each agent to target a different model/provider
with its own capability parameters (vision, context_window, etc.).
- Refactor `_build_agents_table` to return rich dicts instead of tuples
- Extract `_register_one_model` from `_register_unknown_models` for reuse
- Register per-agent models in addition to the global default_model,
falling back to top-level model_capabilities when agent-specific ones
are not provided
- Override `AgentConfig.model` at startup when an agent declares a model
- Thread deployment_config through `_preflight` and `_start_agent`
