Add / @ # commands

I would love to have in-line commands and references with autocomplete like GitHub Copilot in VS Code.

• / = force or strongly suggest a tool/action (ex: /search, /add_memory /code, /summarize)

• @ = target a tool provider

• # = reference artifacts, files, etc.

A clean autocomplete mechanism really makes this feature useful, but would probably require tagging each option with identifiers (e.g., ‘openai:web_search’, ‘boltai:web_fetch’).