Capture: Enter-to-start + on-board notice; dismiss discards a new note

Live-pass feedback: make the "waiting for input" state visible and starting
a note more deliberate, and let dismiss cancel an accidental note.

- New notes are now a confirm-to-keep dialog: Esc OR click-away DISCARD a
  brand-new, not-yet-persisted note (so an accidental keystroke / type-to-
  compose never litters); Ctrl/Cmd+Enter, the footer button, or Shift+Enter
  commit it. A compose already persisted by a rich action, and any existing
  note, still close-and-save on dismiss. The compose footer button is now a
  filled "Add note" so the save path is unmistakable.
- Enter (board, nothing focused) starts a new note; a subtle dashed on-board
  notice — "Press Enter or start typing to add a note" — makes capture
  discoverable instead of silent (click it to compose too). Type-to-compose
  stays as the fast path.
- Empty-state copy + shortcuts help updated (Enter/c for a new note).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/views/BoardView.vue

@@ -94,7 +94,14 @@ function onBoardKey(e: KeyboardEvent) {
     moveFocus(-1);
     return;
   }
-  if (!browsing) return; // resting → let AppShell's type-to-compose take the key
+  if (!browsing) {
+    // Resting: Enter starts a new note; other keys fall to AppShell's type-to-compose.
+    if (key === "Enter") {
+      e.preventDefault();
+      ui.requestCompose();
+    }
+    return;
+  }
   if (key === "Escape") {
     e.preventDefault();
     focusedIndex.value = -1; // leave browse mode, back to type-to-capture
@@ -135,7 +142,7 @@ const emptyState = computed(() => {
   if (currentView.value === "archived")
     return { title: "Nothing archived", subtitle: "Archived notes are tucked away here." };
   if (currentLabel.value) return { title: "No notes with this label", subtitle: "Tag a note to see it here." };
-  return { title: "No notes yet", subtitle: "Hit + New — or just start typing — to capture a thought." };
+  return { title: "No notes yet", subtitle: "Your captured thoughts will show up here." };
 });
 
 async function reload() {
@@ -199,6 +206,16 @@ async function onDrop(target: Note) {
 
 <template>
   <div class="mx-auto w-full max-w-6xl px-4 py-6">
+    <button
+      v-if="isMainBoard"
+      type="button"
+      class="mx-auto mb-4 block w-full max-w-xl rounded-xl border border-dashed border-neutral-300 px-4 py-2.5 text-center text-sm text-neutral-400 transition hover:border-neutral-400 hover:text-neutral-600 focus:outline-none focus-visible:ring-2 focus-visible:ring-brand dark:border-neutral-700 dark:hover:border-neutral-500"
+      @click="ui.requestCompose()"
+    >
+      Press
+      <kbd class="mx-0.5 rounded border border-neutral-300 px-1 text-xs dark:border-neutral-600">Enter</kbd>
+      or start typing to add a note
+    </button>
     <FilterBar v-if="isMainBoard" />
 
     <div v-if="notes.loading" class="py-24 text-center text-sm text-neutral-400">Loading…</div>