shell.css: codify body + .wd-shell + .wd-main as a primitive (fix dead-space layout bug)

services/web-ui/src/css/components/shell.css

@@ -0,0 +1,61 @@
+/* shell.css ─ root document + app shell primitives.
+ *
+ * Defines the html/body baseline AND the .wd-shell horizontal layout
+ * (sidebar + main pane). Every authenticated app page mounts inside
+ * .wd-shell; this is the only correct way to lay out the app.
+ *
+ * History: pre-shell.css, each page rolled its own
+ *   body { margin: 0; } .wd-shell { display: flex; min-height: 100vh; }
+ * inline. Pages that forgot rendered with the sidebar stacking on top
+ * of the content (8px default body margin + display:block .wd-shell),
+ * which read as "dead space at top, left-shifted content at bottom".
+ * Codifying it here prevents that footgun.
+ */
+
+html, body {
+  height: 100%;
+}
+
+body {
+  margin: 0;
+  background: var(--bg-base);
+  color: var(--text-primary);
+  font-family: var(--font);
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+/* App shell: sidebar (fixed width) + main pane (flex-fills viewport).
+ * 100dvh handles mobile chrome resize; 100vh as fallback. */
+.wd-shell {
+  display: flex;
+  min-height: 100vh;
+  min-height: 100dvh;
+  width: 100%;
+}
+
+/* Default main-pane container. Pages may override background/scroll,
+ * but the sizing contract is fixed: fill remaining horizontal space,
+ * scroll vertically, never escape viewport horizontally. */
+.wd-main {
+  flex: 1;
+  min-width: 0;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+  overflow-x: hidden;
+  overflow-y: auto;
+  background: var(--bg-base);
+}
+
+/* Content wrapper inside .wd-main. Caps width for readability on
+ * ultrawide displays; --full opts out for dense data pages. */
+.wd-content {
+  flex: 1;
+  width: 100%;
+  max-width: 1440px;
+  margin: 0 auto;
+  padding: 24px 32px;
+}
+.wd-content--full   { max-width: none; padding: 0; }
+.wd-content--narrow { max-width: 780px; }