Support slash command autocomplete when '/' is typed mid-prompt

Summary

Claude Code only shows slash command suggestions when / is the first character in the input box.

If / is typed in the middle of an otherwise normal prompt, it is treated as plain text and no slash command menu appears.

Why this is useful

Other tools such as Cursor support inline / command discovery while writing a prompt, which makes command usage feel more natural and reduces context switching.

For example, this currently does not trigger suggestions:

Please help review this change /review

Only this does:

/review

Expected behavior

If / is typed in the middle of the input, Claude Code should optionally surface slash command suggestions there as well, or provide a configurable setting to enable inline slash command autocomplete.

Actual behavior

Slash command suggestions only appear when the input starts with /.

Additional context

I found earlier related requests such as #13073 and #29752, but the capability still does not appear to exist today. Reopening the request here because this workflow remains useful and matches how some users expect command discovery to work.