Need tooltip for Leo's slash-tools icon

[stephendonner]

Description

Need tooltip for Leo's slash-tools icon

Found while testing #37294

Steps to Reproduce

1. install 1.68.14
2. launch Brave
3. open a new-tab page
4. click on Leo in the sidebar
5. type test
6. click I understand
7. hover over the [ / ] icon in the Enter a prompt here input box

Actual result:

No tooltip on hover

Expected result:

Appropriate tooltip appears on hover, like this Send message to Leo one for the paper-airplane icon to its right

Reproduces how often:

100%

Brave version (brave://version info)

Brave | 1.68.14 Chromium: 125.0.6422.41 (Official Build) nightly (x86_64)
-- | --
Revision | b2b820a3f51cde3fbd10db0cb93be8a00642c5bb
OS | macOS Version 14.5 (Build 23F79)

cc @aguscruiz @mattmcalister @nullhook @brave/qa-team