Slash command picker doesn't work on multiline input

[0xSkybreaker]

Problem

The slash command picker (/) only triggers on the first line of multiline input. When typing on any line other than the first, the picker does not appear.

Steps to reproduce

1. Type multiple lines of text in the prompt input
2. On any line other than the first, type / followed by characters
3. The slash command picker does not show up

Expected behavior

The slash command picker should appear when / is typed at the beginning of any line, just like @ mention picker works on any line.

Cause

The regex /^\/(\S*)$/ matches against the full rawText instead of just the text up to the cursor position.

[github-actions]

This issue might be a duplicate of an existing issue. Please check:

• [Web UI] Slash command / skill picker only triggers at position 0 - does not open on subsequent lines #34693: Same bug — slash command / skill picker only triggers at position 0 and does not open on subsequent lines of multiline input

If this is the same issue, please consider closing this one and adding any additional context to #34693 instead.