fix: broaden connection error detection for main page and sidepanel (#563)

* fix: broaden connection error detection for main page and sidepanel

The connection error check required both "Failed to fetch" AND
"127.0.0.1" in the error message. On the main page, the browser
only produces "Failed to fetch" without the IP, so users saw a
generic "Something went wrong" instead of the troubleshooting link.

Broaden detection to also match "localhost" and bare "Failed to fetch"
errors that don't contain an external URL. Also pass providerType in
NewTabChat so provider-specific errors render correctly.

Closes #526

* fix: simplify connection error detection

All chat requests go through the local BrowserOS agent server, so any
"Failed to fetch" error is always a local connection issue. Remove the
unnecessary 127.0.0.1/localhost/URL checks.

* fix: pass providerType to agentUrlError ChatError instances

packages/browseros-agent/apps/agent/entrypoints/newtab/index/NewTabChat.tsx

@@ -169,8 +169,15 @@ export const NewTabChat: FC = () => {
             onDismissJtbdPopup={() => {}}
           />
         )}
-        {agentUrlError && <ChatError error={agentUrlError} />}
-        {chatError && <ChatError error={chatError} />}
+        {agentUrlError && (
+          <ChatError
+            error={agentUrlError}
+            providerType={selectedProvider?.type}
+          />
+        )}
+        {chatError && (
+          <ChatError error={chatError} providerType={selectedProvider?.type} />
+        )}
       </main>
 
       <div className="mx-auto w-full max-w-3xl flex-shrink-0 px-4 pb-2">

packages/browseros-agent/apps/agent/entrypoints/sidepanel/index/Chat.tsx

@@ -224,7 +224,12 @@ export const Chat = () => {
             onDismissJtbdPopup={onDismissJtbdPopup}
           />
         )}
-        {agentUrlError && <ChatError error={agentUrlError} />}
+        {agentUrlError && (
+          <ChatError
+            error={agentUrlError}
+            providerType={selectedProvider?.type}
+          />
+        )}
         {chatError && (
           <ChatError error={chatError} providerType={selectedProvider?.type} />
         )}

packages/browseros-agent/apps/agent/entrypoints/sidepanel/index/ChatError.tsx

@@ -34,11 +34,9 @@ function parseErrorMessage(
 } {
   const isBrowserosProvider = providerType === 'browseros'
 
-  // Detect MCP server connection failures (universal — affects all providers)
-  if (
-    (message.includes('Failed to fetch') || message.includes('fetch failed')) &&
-    message.includes('127.0.0.1')
-  ) {
+  // All chat requests go through the local BrowserOS agent server, so any
+  // fetch failure is always a local connection issue.
+  if (message.includes('Failed to fetch') || message.includes('fetch failed')) {
     return {
       text: 'Unable to connect to BrowserOS agent. Follow below instructions.',
       url: 'https://docs.browseros.com/troubleshooting/connection-issues',