feat: editor font-size match, hot model default, Shift-H/L nav

- .cm-editor pinned to font-size 1rem so the input matches the
  output pane (CodeMirror 6 defaults smaller)
- refreshLoaded(isInitial=true) on first load picks the hot model
  as the dropdown default — avoids the 5-15s disk reload on the
  first translation. Subsequent refreshes don't override the user's
  manual selection.
- document-level Shift-H / Shift-L cycle focus across controls
  (source → target → model → editor → button), suppressed when
  focus is inside CodeMirror so vim's viewport H/L still work.

static/index.html

@@ -163,6 +163,7 @@
       border-radius: 6px;
       background: var(--panel);
       font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
+      font-size: 1rem;   /* match .output's inherited body size — CM6 defaults are smaller */
     }
     .cm-editor.cm-focused {
       outline: none;
@@ -428,7 +429,7 @@
       return `${secs}s`;
     }
 
-    async function refreshLoaded() {
+    async function refreshLoaded(isInitial = false) {
       let models = [];
       try {
         const r = await fetch("/api/loaded");
@@ -444,6 +445,7 @@
       const loadedMap = new Map(models.map(m => [m.name, m.expires_at]));
 
       // Update dropdown options. Use textContent (option doesn't render HTML).
+      const optionValues = Array.from(modelSel.options, o => o.value);
       for (const opt of modelSel.options) {
         if (loadedMap.has(opt.value)) {
           opt.textContent = `● ${opt.value}`;
@@ -452,6 +454,14 @@
         }
       }
 
+      // On the very first refresh after page load, prefer a hot model as the
+      // dropdown default — skipping disk reload pain. Only on initial load,
+      // so the user's manual selection isn't yanked away while they type.
+      if (isInitial) {
+        const hot = models.find(m => optionValues.includes(m.name));
+        if (hot) modelSel.value = hot.name;
+      }
+
       // Update status line.
       if (models.length === 0) {
         hotStatus.classList.add("idle");
@@ -468,8 +478,35 @@
 
     goBtn.addEventListener("click", translate);
 
+    // Shift-H / Shift-L navigate focus across controls (vim-style Shift-Tab /
+    // Tab). Skipped when focus is inside the CodeMirror editor — there H/L
+    // are vim's viewport motions and must reach the editor untouched.
+    const focusables = [
+      { el: sourceSel, focus: () => sourceSel.focus() },
+      { el: targetSel, focus: () => targetSel.focus() },
+      { el: modelSel,  focus: () => modelSel.focus()  },
+      { el: editor.contentDOM, focus: () => editor.focus() },
+      { el: goBtn,     focus: () => goBtn.focus()     },
+    ];
+    document.addEventListener("keydown", (e) => {
+      if (!e.shiftKey) return;
+      const k = e.key.toLowerCase();
+      if (k !== "h" && k !== "l") return;
+      if (editor.dom.contains(document.activeElement)) return;  // vim owns H/L in the editor
+      e.preventDefault();
+      const ae = document.activeElement;
+      let idx = focusables.findIndex(f => f.el === ae);
+      if (idx === -1) {
+        focusables[k === "l" ? 0 : focusables.length - 1].focus();
+        return;
+      }
+      const delta = k === "l" ? 1 : -1;
+      const next = focusables[(idx + delta + focusables.length) % focusables.length];
+      next.focus();
+    });
+
     fillLangs();
-    loadModels().then(refreshLoaded);
+    loadModels().then(() => refreshLoaded(true));
   </script>
 </body>
 </html>