Stage 7 polish (round 3): zoom magnifies labels, popover edge-anchor, flash x2

- item 5: move container-type to the zoom-scaled .scaler so cqw labels grow WITH the board (magnifying-glass zoom); new e2e measures the font grows ~1.85x
- item 8: confirm popovers anchor to the trigger's right edge (no longer run off-screen)
- item 9: last-word flash runs 2 cycles then settles to normal (was infinite)

ui/src/components/HoldConfirm.svelte

@@ -92,8 +92,7 @@
   .popover {
     position: absolute;
     bottom: calc(100% + 6px);
-    left: 50%;
-    transform: translateX(-50%);
+    right: 0;
     z-index: 19;
     display: flex;
     flex-direction: column;

ui/src/game/Board.svelte

@@ -84,7 +84,7 @@
             class="cell {premClass[premium[r][c]]}"
             class:filled={!!cell}
             class:pending={!!p && !cell}
-            class:hl={!!cell && highlight.has(key(r, c))}
+            class:hl={!!cell && highlight.has(key(r, c)) && !flash}
             class:flash={!!cell && flash && highlight.has(key(r, c))}
             data-cell
             data-row={r}
@@ -115,14 +115,16 @@
     overflow: hidden;
     background: var(--board-bg);
     border-radius: var(--radius-sm);
-    container-type: inline-size;
   }
   .viewport.zoomed {
     overflow: auto;
   }
+  /* The query container is the (zoom-scaled) board, so cqw labels scale WITH the board
+     — a magnifying-glass zoom. */
   .scaler {
     width: calc(100% * var(--z));
     transition: width 0.25s ease;
+    container-type: inline-size;
   }
   .grid {
     display: grid;
@@ -167,7 +169,8 @@
     background: var(--tile-recent);
   }
   .cell.flash {
-    animation: tileflash 1s ease-in-out infinite;
+    /* Two flashes to draw the eye, then settle back to normal so it does not distract. */
+    animation: tileflash 1s ease-in-out 2;
   }
   @keyframes tileflash {
     0%,