polish: route PGN-error alerts through the in-app dialog too

Replaces the last native alert() calls (corrupted saved game / unparseable PGN)
and the delete confirm with the same <dialog>-based modalAlert/modalConfirm
helpers, so no flow relies on native popups that the browser may suppress.
Bump cache version.

src/chess_pressure/static/app.js

@@ -347,7 +347,7 @@
     try {
       parsed = ChessPressure.parsePgn(g.pgn);
     } catch (e) {
-      alert("That saved game could not be loaded (corrupted PGN).");
+      modalAlert("That saved game could not be loaded (corrupted PGN).", "Couldn't load game");
       return;
     }
     applyParsed(parsed, savedId, true);
@@ -360,7 +360,7 @@
     try {
       parsed = ChessPressure.parsePgn(pgn);
     } catch (e) {
-      alert("Could not parse PGN — please check the format and try again.");
+      modalAlert("Could not parse PGN — please check the format and try again.", "Couldn't parse PGN");
       return;
     }
     applyParsed(parsed, null, isReference);
@@ -458,6 +458,28 @@
     });
   }
 
+  // Yes/no confirmation via the in-app dialog. Resolves true (OK) / false (cancel).
+  function modalConfirm(message, title) {
+    const dlg = document.getElementById("confirm-dialog");
+    document.getElementById("confirm-title").textContent = title || "Please confirm";
+    document.getElementById("confirm-msg").textContent = message;
+    dlg.querySelector("[data-cancel]").style.display = "";
+    return openModal(dlg);
+  }
+
+  // Single-button notice via the in-app dialog (replaces native alert()).
+  function modalAlert(message, title) {
+    const dlg = document.getElementById("confirm-dialog");
+    document.getElementById("confirm-title").textContent = title || "Notice";
+    document.getElementById("confirm-msg").textContent = message;
+    const cancel = dlg.querySelector("[data-cancel]");
+    cancel.style.display = "none";
+    return openModal(dlg).then((v) => {
+      cancel.style.display = "";
+      return v;
+    });
+  }
+
   async function saveCurrentGame() {
     if (!gameData) return;
     const dlg = document.getElementById("save-dialog");
@@ -502,8 +524,7 @@
     if (!currentSavedId) return;
     const g = getSavedGames().find((x) => x.id === currentSavedId);
     if (!g) return;
-    document.getElementById("confirm-msg").textContent = `Delete saved game "${g.name}"?`;
+    const ok = await modalConfirm(`Delete saved game "${g.name}"?`, "Delete game");
-    const ok = await openModal(document.getElementById("confirm-dialog"));
     if (!ok) return;
     setSavedGames(getSavedGames().filter((x) => x.id !== currentSavedId));
     currentSavedId = null;

src/chess_pressure/static/index.html

@@ -4,7 +4,7 @@
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Chess Pressure</title>
-  <link rel="stylesheet" href="/style.css?v=29">
+  <link rel="stylesheet" href="/style.css?v=30">
   <link rel="stylesheet" href="https://unpkg.com/@chrisoakman/chessboardjs@1.0.0/dist/chessboard-1.0.0.min.css">
   <link rel="manifest" href="/manifest.json">
 </head>
@@ -137,7 +137,7 @@
 
   <dialog id="confirm-dialog">
     <form method="dialog">
-      <h2>Please confirm</h2>
+      <h2 id="confirm-title">Please confirm</h2>
       <p id="confirm-msg" class="export-info"></p>
       <div class="dialog-buttons">
         <button type="button" data-ok>OK</button>
@@ -164,6 +164,6 @@
   <script src="/chess.min.js"></script>
   <script src="/gif.js"></script>
   <script src="/engine.js"></script>
-  <script src="/app.js?v=29"></script>
+  <script src="/app.js?v=30"></script>
 </body>
 </html>

src/chess_pressure/static/sw.js

@@ -7,7 +7,7 @@
  *
  * Bump CACHE on every deploy so clients pick up new assets.
  */
-const CACHE = "chess-pressure-v29";
+const CACHE = "chess-pressure-v30";
 
 // Same-origin app shell. Cached by canonical path; the fetch handler matches
 // with ignoreSearch so cache-busting query strings (?v=NN) still hit.