Remove checkmarks from chat-used-context-label, add hover chevron

[daviddossett]

Remove checkmark icons from chat-used-context-label elements and replace with a hover chevron indicator that points down when expanded.

Changes:

• chatCollapsibleContentPart.ts: Hide leading icon unless it's an error/warning; add hover chevron element that toggles direction on expand/collapse
• chatToolInputOutputContentPart.ts: Same treatment — only show error icon, hide checkmark/loading; add hover chevron
• chat.css: Adjust gap to 0, add margin-left: -2px to compensate for removed icon, update hover styles, add .chat-collapsible-hover-chevron CSS rules (hidden by default, visible on hover or when expanded)

[Copilot]

Pull request overview

This PR updates the chat UI for collapsible “used context” and tool input/output headers by removing the leading checkmark/loading icons and introducing a subtle chevron indicator that appears on hover and flips direction when expanded.

Changes:

• Hide leading icons for collapsible chat headers unless they represent an error/warning state.
• Add a right-side hover chevron to indicate expand/collapse state and update it reactively.
• Adjust chat CSS spacing/hover styles and introduce .chat-collapsible-hover-chevron styling.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
src/vs/workbench/contrib/chat/browser/widget/media/chat.css	Updates button spacing and adds styles for the new hover chevron indicator.
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatToolInputOutputContentPart.ts	Adds chevron indicator to tool IO collapsible header and removes non-error leading icons.
src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatCollapsibleContentPart.ts	Adds chevron indicator to used-context collapsible header and hides non-error/warning leading icons.

Comments suppressed due to low confidence (2)

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/chatCollapsibleContentPart.ts:92

• setupDelayedHover is attached to collapseButton.iconElement, but this PR hides iconElement for non-error/warning states. That makes hoverMessage effectively unreachable in the common case. Consider anchoring the hover on collapseButton.element (or the new chevron) instead of the icon element.

		if (this.hoverMessage) {
			this._register(this.hoverService.setupDelayedHover(collapseButton.iconElement, {
				content: this.hoverMessage,
				style: HoverStyle.Pointer,
			}));

src/vs/workbench/contrib/chat/browser/widget/media/chat.css:2201

• .interactive-session ... .monaco-button .codicon { color: ... !important; } will override the intended color for .chat-collapsible-hover-chevron (which is also a .codicon) inside used-context labels. If the chevron is supposed to use --vscode-descriptionForeground, consider excluding .chat-collapsible-hover-chevron from this rule or increasing specificity/using !important on the chevron color.

.interactive-session .chat-file-changes-label .monaco-button .codicon,
.interactive-session .chat-used-context-label .monaco-button .codicon {
	font-size: 12px;
	color: var(--vscode-icon-foreground) !important;
}