Alias to `/` to `$` when an existing command does not resolve

Allow the TUI to automatically resolve toward known skills when /[token] is unmatched.

Pass-through complete autocomplete experience enjoyed from proper $[token] use.

Reasoning:

• Presumably data shows skills vastly outweigh command use at this time.
• If a user is being captured from CC, they will not know about $. Muscle memory is attuned to /. And the memory is strong.
• Current TUI rejects CC-valid skill invocation as per #17796
• This rejection actually makes it look like the product doesn't know about skills! At very least, output should provide a hint toward skill invocation, as again data probably shows the amount of failed "command" invocations are largely skill invocation attempts.

I am a long time codex user (as much as that can be) and did not know about it until @etraut-openai specified here.