feat(client): phantom-piece palette component

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/client/src/lib/PhantomPalette.svelte

@@ -0,0 +1,50 @@
+<script lang="ts">
+  import type { Color, PieceType } from '@blind-chess/shared';
+  import { pieceGlyph } from './pieces.js';
+  import { phantomDrag } from './stores/phantom-drag.svelte.js';
+
+  interface Props { oppColor: Color; }
+  let { oppColor }: Props = $props();
+
+  const TYPES: PieceType[] = ['q', 'r', 'b', 'n', 'p', 'k'];
+</script>
+
+<div class="palette">
+  <span class="hint muted">Drag onto your board — your guess of where the opponent is.</span>
+  <div class="pieces">
+    {#each TYPES as t (t)}
+      <!-- Pointer-only drag source — same deliberate a11y trade-off as the
+           phantom spans in Board.svelte (no keyboard drag interaction). -->
+      <!-- svelte-ignore a11y_no_static_element_interactions -->
+      <span
+        class="pp pp-{oppColor}"
+        onpointerdown={(e) => { e.preventDefault(); phantomDrag.start({ kind: 'palette', type: t }, e); }}
+      >{pieceGlyph({ color: oppColor, type: t })}</span>
+    {/each}
+  </div>
+</div>
+
+<style>
+  .palette {
+    display: flex;
+    flex-direction: column;
+    gap: 4px;
+    background: var(--panel);
+    border: 1px solid var(--border);
+    border-radius: 8px;
+    padding: 8px 12px;
+  }
+  .hint { font-size: 12px; }
+  .pieces { display: flex; gap: 6px; }
+  .pp {
+    font-size: 30px;
+    line-height: 1;
+    cursor: grab;
+    touch-action: none;
+    opacity: 0.75;
+    user-select: none;
+  }
+  .pp:hover { opacity: 1; }
+  .pp-w { color: #fafafa; }
+  .pp-b { color: #1a1a1a; }
+</style>