fix(odin): measured --app-height for standalone-PWA viewports

Installed PWAs (MIUI especially) compute svh/dvh against a viewport that
includes system UI the layout viewport doesn't have, so the immersive page
still scrolled in standalone mode. AppShell now measures window.innerHeight
into --app-height (refreshed on resize/visualViewport, covering the
minimize-restore stale-viewport Chrome bug and the keyboard), and the
immersive shell + chat size from var(--app-height, 100svh).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/admin/components/odin/OdinChat.tsx

@@ -437,8 +437,13 @@ export default function OdinChat() {
         // page never scrolls and the chat's message list scrolls internally.
         // Desktop: svh === vh.
         // Mobile is immersive (AppShell hides its header and main padding on
-        // /odin): the chat owns the whole viewport, full-bleed.
-        height: { xs: "100svh", md: "calc(100svh - 100px)" },
+        // /odin): the chat owns the whole viewport, full-bleed. --app-height
+        // is AppShell's live window.innerHeight measurement — standalone-PWA
+        // viewports misreport svh/dvh (MIUI), only the measured value fits.
+        height: {
+          xs: "var(--app-height, 100svh)",
+          md: "calc(100svh - 100px)",
+        },
         display: "flex",
         // Longhand on purpose: a responsive `border` shorthand lands in a
         // media query AFTER borderColor and resets the color to black.