fix: pass Models map to RAG ManagersBuildConfig for model alias resolution

[dgageot]

Problem

createRAGTool in pkg/teamloader/registry.go builds rag.ManagersBuildConfig without populating the Models field. This means any RAG config using a model alias for reranking (e.g. model: balanced referencing a named model from the top-level models: section) fails at runtime with:

toolset rag failed: failed to create RAG manager: failed to build manager
config for RAG "rag": failed to build reranking config: failed to resolve
reranking model "balanced": model "balanced" not found in configuration

Fix

• Add Models field to config.Config
• Populate runConfig.Models from cfg.Models in teamloader before agent loading
• Pass runConfig.Models through to ManagersBuildConfig in createRAGTool
• Clone Models map in RuntimeConfig.Clone() to prevent shared mutable state
• Add tests for Models cloning isolation