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/config.test.ts

@@ -50,6 +50,25 @@ describe("layersToConfigs", () => {
     });
   });
 
+  test("parses combined vertical+horizontal align", () => {
+    const layers = layersToConfigs([
+      { prop: "a", pos: "1,1-2,2", align: "tl" },
+      { prop: "b", pos: "1,1-2,2", align: "br" },
+      { prop: "c", pos: "1,1-2,2", align: "tc" },
+      { prop: "d", pos: "1,1-2,2", align: "bc" },
+    ]);
+    expect(layers[0].align).toBe("tl");
+    expect(layers[1].align).toBe("br");
+    expect(layers[2].align).toBe("tc");
+    expect(layers[3].align).toBe("bc");
+  });
+
+  test("parses vertical+horizontal align in compact layers string", () => {
+    const layers = layersToConfigs("title:1,1-4,1tl body:1,2-5,8bc");
+    expect(layers[0].align).toBe("tl");
+    expect(layers[1].align).toBe("bc");
+  });
+
   test("defaults placement when pos is missing or invalid", () => {
     const layers = layersToConfigs([{ prop: "x" }, { prop: "y", pos: "bogus" }]);
     expect(layers[0]).toMatchObject({ x1: 1, y1: 1, x2: 2, y2: 2 });