feat: open chat panel from /open when agentId param is present

The existing /open deep link now optionally accepts an agentId query
parameter. When present, the chat panel opens alongside the workspace.
Old extensions silently ignore unknown query params, so this is fully
backwards compatible — no error dialog, no version negotiation needed.

The standalone /openChat route is kept for cases where no workspace
context is needed (e.g. direct links from the agents page).

Author: ThomasK33

src/uri/uriHandler.ts

@@ -91,7 +91,13 @@ function getRequiredParam(params: URLSearchParams, name: string): string {
 }
 
 async function handleOpen(ctx: UriRouteContext): Promise<void> {
-	const { params, serviceContainer, deploymentManager, commands } = ctx;
+	const {
+		params,
+		serviceContainer,
+		deploymentManager,
+		commands,
+		chatPanelProvider,
+	} = ctx;
 
 	const owner = getRequiredParam(params, "owner");
 	const workspace = getRequiredParam(params, "workspace");
@@ -101,6 +107,11 @@ async function handleOpen(ctx: UriRouteContext): Promise<void> {
 		params.has("openRecent") &&
 		(!params.get("openRecent") || params.get("openRecent") === "true");
 
+	// Optional: if agentId is present, also open the embedded chat
+	// panel. Old extensions silently ignore this unknown param,
+	// giving backwards compatibility.
+	const agentId = params.get("agentId");
+
 	await setupDeployment(params, serviceContainer, deploymentManager);
 
 	await commands.open(
@@ -110,6 +121,10 @@ async function handleOpen(ctx: UriRouteContext): Promise<void> {
 		folder ?? undefined,
 		openRecent,
 	);
+
+	if (agentId) {
+		chatPanelProvider.openChat(agentId);
+	}
 }
 
 async function handleOpenDevContainer(ctx: UriRouteContext): Promise<void> {