Fix: server URL and password fields ignored typing

The Enter-key handlers were expression-bodied arrows assigned to DOM on…
properties: `(e) => e.key === "Enter" && submit()` returns false for every
other key, and an on… handler returning false cancels the event, so the
server URL ("Use my phone") and both master-password fields accepted no input.
Use block bodies, and add scripts/check-handlers.mjs (run by npm run build)
to fail the build on handlers that can return false.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/main.ts

@@ -122,7 +122,10 @@ function phonePanel(body: HTMLElement, status: SyncStatus) {
       start.disabled = false;
     }
   };
-  url.onkeydown = (e) => e.key === "Enter" && start.click();
+  // Block body on purpose: a DOM `on…` handler that returns `false` cancels the event, which would block typing.
+  url.onkeydown = (e) => {
+    if (e.key === "Enter") start.click();
+  };
   if (!url.value) url.focus();
 }
 
@@ -255,7 +258,9 @@ function finishSetup(body: HTMLElement, view: SetupView) {
     btn.disabled = false;
   };
   btn.onclick = submit;
-  pw.onkeydown = (e) => e.key === "Enter" && void submit();
+  pw.onkeydown = (e) => {
+    if (e.key === "Enter") void submit();
+  };
   body.replaceChildren(
     el("p", {}, "Signing in to ", el("strong", { textContent: view.server_host }), "."),
     el("p", { className: "muted", textContent: view.preapproved ? "This computer is pre-approved." : "Another device will need to approve this computer." }),
@@ -339,7 +344,9 @@ function renderUnlock(state: AppState) {
     }
   };
   btn.onclick = submit;
-  pw.onkeydown = (e) => e.key === "Enter" && void submit();
+  pw.onkeydown = (e) => {
+    if (e.key === "Enter") void submit();
+  };
   const card = el("div", { className: "card" }, el("h2", { textContent: "Kestrove is locked" }), pw);
   if (!state.remembers_secret_key) card.append(sk);
   card.append(btn, err);