/model picker should show all available models

Problem

The /model interactive picker only shows a curated subset of available models. For example, claude-opus-4-6 is a valid model that works with /model claude-opus-4-6, but it doesn't appear in the picker list.

This means users don't know what's available unless they already know the model IDs. There's no --all flag or configuration option to show the full list.

Expected behavior

The /model picker should list all models available to the user's account, not a curated subset. The model family is small — there's no UX reason to hide options.

Workaround

Users must type /model <model-id> directly with the exact model ID, but there's no way to discover valid IDs from within Claude Code itself.

Suggestion

Either:

1. Show all available models in the picker by default, or
2. Add a configuration option / flag (e.g., /model --all) to display the full list