marketing: avoid double cast in copy-button analytics

The clipboard handler now asks for a capture via a DOM event (analytics:capture) that the gated PostHog init listens for, instead of reaching through a window double cast. Fixes the lint rule that banned casting through unknown.

Author: RhysSullivan

apps/marketing/src/layouts/Layout.astro

@@ -67,7 +67,17 @@ const canonical = new URL(Astro.url.pathname, Astro.site ?? Astro.url).toString(
             capture_pageview: false,
             persistence: "localStorage",
           });
-          Object.assign(window, { posthog });
+          // The copy handler (in index.astro) is a separate bundle, so it asks
+          // for a capture via a DOM event rather than reaching for a global.
+          window.addEventListener("analytics:capture", (e) => {
+            const detail = (
+              e as CustomEvent<{
+                event: string;
+                properties?: Record<string, unknown>;
+              }>
+            ).detail;
+            posthog.capture(detail.event, detail.properties);
+          });
         });
       }
     </script>

apps/marketing/src/pages/index.astro

@@ -442,13 +442,11 @@ Source (and the place to start if something breaks): https://github.com/RhysSull
           btn.dataset.copied = "true";
           const event = btn.dataset.event;
           if (event) {
-            (
-              window as unknown as {
-                posthog?: {
-                  capture: (e: string, p?: Record<string, unknown>) => void;
-                };
-              }
-            ).posthog?.capture(event, { surface: "marketing_hero" });
+            window.dispatchEvent(
+              new CustomEvent("analytics:capture", {
+                detail: { event, properties: { surface: "marketing_hero" } },
+              }),
+            );
           }
         } catch {
           btn.dataset.copied = "false";