feat(lightspeed): fullscreen chat UX updates - history panel, message bar, and header redesign

[its-mitesh-kumar]

Summary

This PR implements comprehensive UI/UX updates for the Lightspeed chat in fullscreen mode, aligning with the Figma mockups.

Fixed

• Fixes https://redhat.atlassian.net/browse/RHDHBUGS-3099

Changes

Header

• Replaced hamburger menu with Lightspeed logo in fullscreen mode
• Updated styling for fullscreen header layout

History Panel

• Added collapsible history panel with expand/collapse functionality
• Created CollapsedHistoryStrip component with:
  • Expand panel icon (arrow pointing right)
  • Quick new chat icon (EditSquare in blue)
• Panel is resizable with defined min/max width constraints
• Three-dot options menu now only visible on hover
• Added pointer cursor on conversation item hover

Message Bar

• Redesigned message bar as a unified gray container
• Moved model selector inside the message bar (bottom-left)
• Created AttachPlusMenu component for attachment functionality (bottom-left)
• Microphone and send buttons positioned at bottom-right
• Entire message bar area is now clickable to focus input
• Text cursor shown when hovering over message bar

Scope

All changes only apply to fullscreen display mode. Overlay and docked modes retain their original styling and functionality.

UI after changes

Screen.Recording.2026-05-06.at.9.11.22.PM.mov

Test Plan

• Open Lightspeed in fullscreen mode
• Verify history panel can be collapsed and expanded
• Verify collapsed strip shows expand and new chat icons
• Verify new chat icon is blue
• Verify message bar has unified gray styling
• Verify model selector and attach menu are at bottom-left
• Verify microphone and send buttons are at bottom-right
• Verify clicking anywhere on message bar focuses the input
• Verify three-dot menu only appears on hover
• Verify overlay and docked modes are unchanged

Figma References

• Fullscreen Chat Design

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or Updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)

[rhdh-gh-app]

Important

This PR includes changes that affect public-facing API. Please ensure you are adding/updating documentation for new features or behavior.

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@red-hat-developer-hub/backstage-plugin-lightspeed	workspaces/lightspeed/plugins/lightspeed	minor	v2.6.6

[its-mitesh-kumar]

/cc @ShiranHi @debsmita1 @karthikjeeyar @HusneShabbir

[codecov]

Codecov Report

❌ Patch coverage is 80.59701% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.82%. Comparing base (3eec62c) to head (0b74421).
⚠️ Report is 9 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3057      +/-   ##
==========================================
+ Coverage   60.80%   60.82%   +0.01%     
==========================================
  Files        2067     2069       +2     
  Lines       63895    63967      +72     
  Branches    16660    16688      +28     
==========================================
+ Hits        38852    38907      +55     
- Misses      24481    24497      +16     
- Partials      562      563       +1     

Flag	Coverage Δ		*Carryforward flag
adoption-insights	83.58% <ø> (ø)		Carriedforward from 2e80921
ai-integrations	70.03% <ø> (ø)		Carriedforward from 2e80921
app-defaults	69.60% <ø> (ø)		Carriedforward from 2e80921
augment	69.36% <ø> (ø)		Carriedforward from 2e80921
bulk-import	72.44% <ø> (ø)		Carriedforward from 2e80921
cost-management	16.49% <ø> (ø)		Carriedforward from 2e80921
dcm	32.85% <ø> (ø)		Carriedforward from 2e80921
extensions	61.71% <ø> (ø)		Carriedforward from 2e80921
global-floating-action-button	73.75% <ø> (ø)		Carriedforward from 2e80921
global-header	61.68% <ø> (ø)		Carriedforward from 2e80921
homepage	50.84% <ø> (ø)		Carriedforward from 2e80921
konflux	91.01% <ø> (ø)		Carriedforward from 2e80921
lightspeed	70.04% <80.59%> (+0.08%)	⬆️
mcp-integrations	81.59% <ø> (ø)		Carriedforward from 2e80921
orchestrator	33.15% <ø> (ø)		Carriedforward from 2e80921
quickstart	62.64% <ø> (ø)		Carriedforward from 2e80921
sandbox	79.56% <ø> (ø)		Carriedforward from 2e80921
scorecard	83.61% <ø> (ø)		Carriedforward from 2e80921
theme	64.54% <ø> (ø)		Carriedforward from 2e80921
translations	8.49% <ø> (ø)		Carriedforward from 2e80921
x2a	82.09% <ø> (ø)		Carriedforward from 2e80921

*This pull request uses carry forward flags. Click here to find out more.

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[ShiranHi]

Thanks @its-mitesh-kumar, great update!
LGTM. One minor fix: align the top and right-hand side paddings of the sidebar across both the collapsed and expanded states to ensure the spacing remains the same:

[its-mitesh-kumar]

I have removed the styles overriding through custom styles. Attaching updated screen recording

Screen.Recording.2026-05-07.at.7.06.34.PM.mov

@karthikjeeyar @ShiranHi

[sonarqubecloud]

Quality Gate failed

Failed conditions
4.1% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud

[its-mitesh-kumar]

Moving collapse icon little bit top right

Screen.Recording.2026-05-08.at.2.58.03.AM.mov