fix: handle fetch failures and stop keying UI logic off display text

- refreshStatus()/observe() now check response.ok and catch fetch
  errors, showing a clear "Connection problem" state instead of
  silently rendering blank/undefined status on a non-2xx response.
- Track session state in a currentState variable (set in
  refreshStatus) and branch the trigger button's click handler on
  currentState === "book_complete" instead of parsing statusEl's
  displayed text, so future copy changes can't silently break the
  next-book/manual-trigger branch.

bookmark/static/app.js

@@ -10,9 +10,33 @@ const STATE_COPY = {
   book_complete: { status: "Book complete!", hint: "Tap Next Book to continue." },
 };
 
+const CONNECTION_ERROR_COPY = {
+  status: "Connection problem — get a volunteer",
+  hint: "The intake station couldn't reach the server. Try again, or ask for help.",
+};
+
+let currentState = null;
+
+function showConnectionError() {
+  currentState = null;
+  statusEl.textContent = CONNECTION_ERROR_COPY.status;
+  hintEl.textContent = CONNECTION_ERROR_COPY.hint;
+}
+
 async function refreshStatus() {
-  const response = await fetch("/api/session-state");
+  let response;
+  try {
+    response = await fetch("/api/session-state");
+  } catch (err) {
+    showConnectionError();
+    return;
+  }
+  if (!response.ok) {
+    showConnectionError();
+    return;
+  }
   const body = await response.json();
+  currentState = body.state;
   const copy = STATE_COPY[body.state] || { status: body.state, hint: "" };
   statusEl.textContent = copy.status;
   hintEl.textContent = copy.hint;
@@ -24,12 +48,21 @@ function refreshPreview() {
 }
 
 async function observe() {
-  await fetch("/api/observe", { method: "POST" });
+  try {
+    const response = await fetch("/api/observe", { method: "POST" });
+    if (!response.ok) {
+      showConnectionError();
+      return;
+    }
+  } catch (err) {
+    showConnectionError();
+    return;
+  }
   await refreshStatus();
 }
 
 triggerButton.addEventListener("click", async () => {
-  if (statusEl.textContent === "Book complete!") {
+  if (currentState === "book_complete") {
     await fetch("/api/next-book", { method: "POST" });
   } else {
     await fetch("/api/manual-trigger", { method: "POST" });