resolves https://github.com/elastic/search-team/issues/13654
resolves https://github.com/elastic/search-team/issues/13761
resolves https://github.com/elastic/search-team/issues/13764

Summary

Commit Make the full chat box as click area Bug: #13654

*** The red box is there to illustrative the clickable area

Commit Add new chat button in collapsed left nav view Bug: #13761

Commit Agent Selector - not respecting the max height of agents Bug: #13764

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines
• Review the backport guidelines and apply applicable backport:* labels.