feat(tables): Indicador ordenación ▴/▾ Unicode en headers

- SortDirection.symbol() ahora retorna ▴/▾ en vez de ^/v
- AdvancedTable usa los mismos glifos Unicode
- VirtualAdvancedTable ya usaba symbol()

src/widgets/advanced_table/advanced_table.zig

@@ -453,12 +453,12 @@ fn drawHeader(
             ctx.pushCommand(Command.text(lookup_x, text_y, "?", Style.Color.primary));
         }
 
-        // Draw sort indicator
+        // Draw sort indicator (▴/▾ Unicode glyphs)
         if (table_state.sort_column == @as(i32, @intCast(idx))) {
-            const indicator_x = col_x + @as(i32, @intCast(col.width)) - 12;
+            const indicator_x = col_x + @as(i32, @intCast(col.width)) - 16;
             const indicator = switch (table_state.sort_direction) {
-                .ascending => "^",
-                .descending => "v",
+                .ascending => "▴",
+                .descending => "▾",
                 .none => "",
             };
             if (indicator.len > 0) {

src/widgets/virtual_advanced_table/types.zig

@@ -23,8 +23,8 @@ pub const SortDirection = enum {
     pub fn symbol(self: SortDirection) []const u8 {
         return switch (self) {
             .none => "",
-            .ascending => " ^",
-            .descending => " v",
+            .ascending => "▴",
+            .descending => "▾",
         };
     }
 };