fix: remove unused collapsed property from WorkspacePanel

The collapsed state is owned by PiWebApp and used only to toggle the
shell CSS class and hide the element — the WorkspacePanel never reads
it. Remove the dead property and its pass-through.

src/client/src/components/PiWebApp.ts

@@ -511,7 +511,7 @@ export class PiWebApp extends LitElement {
     const panelContext = workspace === undefined ? undefined : this.createWorkspacePanelContext(workspace);
     const workspaceLabelItems = workspace === undefined ? [] : this.plugins.getWorkspaceLabelItems(this.state, workspace);
     const emptyState = workspace === undefined ? this.workspacePanelEmptyState() : undefined;
-    return html`<workspace-panel .workspace=${workspace} .panelContext=${panelContext} .emptyState=${emptyState} .tool=${this.state.workspaceTool} .panels=${this.visibleWorkspacePanels()} .workspaceLabelItems=${workspaceLabelItems} .collapsed=${this.state.workspacePanelCollapsed} .onSelectTool=${(tool: QualifiedContributionId) => { this.openWorkspaceTool(tool); }} .onToggleCollapse=${() => { this.toggleWorkspacePanelCollapse(); }}></workspace-panel>`;
+    return html`<workspace-panel .workspace=${workspace} .panelContext=${panelContext} .emptyState=${emptyState} .tool=${this.state.workspaceTool} .panels=${this.visibleWorkspacePanels()} .workspaceLabelItems=${workspaceLabelItems} .onSelectTool=${(tool: QualifiedContributionId) => { this.openWorkspaceTool(tool); }} .onToggleCollapse=${() => { this.toggleWorkspacePanelCollapse(); }}></workspace-panel>`;
   }
 
   private toggleWorkspacePanelCollapse(): void {

src/client/src/components/WorkspacePanel.ts

@@ -19,7 +19,6 @@ export class WorkspacePanel extends LitElement {
   @property({ attribute: false }) panels: QualifiedWorkspacePanelContribution[] = [];
   @property({ attribute: false }) workspaceLabelItems: WorkspaceLabelItem[] = [];
   @property({ type: Boolean }) hideToolTabs = false;
-  @property({ type: Boolean }) collapsed = false;
   @property({ attribute: false }) onSelectTool: (tool: QualifiedContributionId) => void = () => undefined;
   @property({ attribute: false }) onToggleCollapse: () => void = () => undefined;
   @query(".workspace-header-strip") private workspaceHeaderStrip?: HTMLElement | null;