fix(themes): complete summer-day with Everforest Light palette

colors.toml and icons.theme were copy-pasted from summer-night (a dark
theme). Repalette to Everforest Light, mark as light via light.mode,
switch icons to Yaru-blue, fix the broken Waybar import, and add the
btop/neovim/vscode/rofi/walker app configs the sibling themes ship.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

themes/palettes/summer-day/apps/walker/style.css

@@ -0,0 +1,34 @@
+#window {
+    background-color: #fdf6e3;
+    color: #5c6a72;
+    border-bottom: 5px solid #dfa000;
+    border-radius: 15px;
+}
+
+#search {
+    background-color: #8da101;
+    color: #fdf6e3;
+    border-bottom: 5px solid #bdc3af;
+    border-radius: 10px;
+    margin: 15px;
+    padding: 10px;
+}
+
+#input {
+    color: #5c6a72;
+}
+
+#list {
+    padding: 20px;
+}
+
+.item {
+    border-radius: 10px;
+    padding: 10px;
+}
+
+.item.active {
+    background-color: #e6e2cc;
+    color: #5c6a72;
+    border-bottom: 5px solid #bdc3af;
+}