feat(md-deck): add vertical alignment options to layers

Expand align from l/c/r to a 3x3 grid with vertical prefixes:
tl/tc/tr/bl/bc/br. Vertical position renders via flex
justify-content; compact layers strings and YAML both parse the
new values, and the layer editor dropdown gains corner/edge
options.

src/components/md-deck/editor-panel/LayerRow.tsx

@@ -1,7 +1,7 @@
 import { For, createSignal, onCleanup, onMount } from "solid-js";
 import { createSortable, useDragDropContext } from "@thisbeyond/solid-dnd";
 import type { DeckStore } from "../hooks/deckStore";
-import type { LayerConfig } from "../types";
+import type { Align, LayerConfig } from "../types";
 import alignLeftIcon from "./icons/align-left.png";
 import alignCenterIcon from "./icons/align-center.png";
 import alignRightIcon from "./icons/align-right.png";
@@ -17,7 +17,7 @@ export interface LayerRowProps {
   setOpenDropdown: (val: string | null) => void;
   onUpdateOrientation: (o: "n" | "s" | "e" | "w") => void;
   onUpdateFontSize: (fs?: number) => void;
-  onUpdateAlign: (a?: "l" | "c" | "r") => void;
+  onUpdateAlign: (a?: Align) => void;
   onSelect: () => void;
   onRemove: () => void;
 }
@@ -29,11 +29,17 @@ const ORIENTATIONS = [
   { value: "w" as const, label: "← 西" },
 ];
 
-const ALIGNS = [
-  { value: "" as const, icon: alignCenterIcon },
-  { value: "l" as const, icon: alignLeftIcon },
-  { value: "c" as const, icon: alignCenterIcon },
-  { value: "r" as const, icon: alignRightIcon },
+const ALIGNS: { value: Align | ""; icon: string }[] = [
+  { value: "", icon: alignCenterIcon },
+  { value: "l", icon: alignLeftIcon },
+  { value: "c", icon: alignCenterIcon },
+  { value: "r", icon: alignRightIcon },
+  { value: "tl", icon: "↖" },
+  { value: "tc", icon: "↑" },
+  { value: "tr", icon: "↗" },
+  { value: "bl", icon: "↙" },
+  { value: "bc", icon: "↓" },
+  { value: "br", icon: "↘" },
 ];
 
 const FONT_PRESETS = [3, 5, 8, 12] as const;
@@ -53,14 +59,28 @@ function orientChar(v: string) {
   }
 }
 
-function alignSrc(v: string) {
+function alignIcon(v: string): import("solid-js").JSX.Element {
   switch (v) {
+    case "tl":
+      return "↖";
+    case "tc":
+      return "↑";
+    case "tr":
+      return "↗";
+    case "bl":
+      return "↙";
+    case "bc":
+      return "↓";
+    case "br":
+      return "↘";
     case "l":
-      return alignLeftIcon;
+      return <img src={alignLeftIcon} alt="align" class="w-5 h-5 not-prose" />;
     case "r":
-      return alignRightIcon;
+      return <img src={alignRightIcon} alt="align" class="w-5 h-5 not-prose" />;
     default:
-      return alignCenterIcon;
+      return (
+        <img src={alignCenterIcon} alt="align" class="w-5 h-5 not-prose" />
+      );
   }
 }
 
@@ -149,13 +169,7 @@ export function LayerRow(props: LayerRowProps) {
       </DropdownButton>
 
       <DropdownButton
-        icon={
-          <img
-            src={alignSrc(props.layer.align || "")}
-            alt="align"
-            class="w-5 h-5 not-prose"
-          />
-        }
+        icon={alignIcon(props.layer.align || "")}
         visible={props.layer.visible}
         open={props.openDropdown === `align-${props.index}`}
         onToggle={() =>
@@ -173,7 +187,13 @@ export function LayerRow(props: LayerRowProps) {
               onClick={() => props.onUpdateAlign(o.value || undefined)}
               class="flex items-center gap-2 w-full px-3 py-1.5 text-sm hover:bg-gray-100 cursor-pointer whitespace-nowrap"
             >
-              <img src={o.icon} alt="" class="w-4 h-4 not-prose max-w-none" />
+              {o.icon.endsWith(".png") ? (
+                <img src={o.icon} alt="" class="w-4 h-4 not-prose max-w-none" />
+              ) : (
+                <span class="w-4 h-4 flex items-center justify-center not-prose">
+                  {o.icon}
+                </span>
+              )}
             </button>
           )}
         </For>