Resolves pi-internal:// paths to the coding-agent package directory,
allowing the model to read internal documentation. Appends a hint
showing the filesystem path and instructing to use it for further reads.
- /model <search> pre-filters selector or auto-selects on exact match
- Support provider/model syntax for disambiguation (e.g., /model openai/gpt-4)
- Auto-select logic moved to InteractiveMode to avoid selector UI flicker
Closes#587
Mario Zechner