fix(admin): use collection urlPattern for preview button fallback URL (#181)

* fix(admin): use collection urlPattern for preview button fallback URL

The preview button hardcoded fallback URLs as /${collection}/${slug},
ignoring the collection's urlPattern setting. Collections with custom
URL patterns (e.g. urlPattern: "/biljke/{slug}" on a "biljka" collection)
would open a 404 instead of the correct page.

Thread urlPattern through the manifest and use it in the ContentEditor
preview fallback.

Fixes #167

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Signed-off-by: Filip Ilic <ilic.filip@gmail.com>

* chore: add changeset for preview URL pattern fix

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Signed-off-by: Filip Ilic <ilic.filip@gmail.com>

---------

Signed-off-by: Filip Ilic <ilic.filip@gmail.com>
Co-authored-by: Matt Kane <mkane@cloudflare.com>

packages/core/src/astro/types.ts

@@ -28,6 +28,7 @@ export interface ManifestCollection {
 	labelSingular: string;
 	supports: string[];
 	hasSeo: boolean;
+	urlPattern?: string;
 	fields: Record<
 		string,
 		{

packages/core/src/emdash-runtime.ts

@@ -1180,6 +1180,7 @@ export class EmDashRuntime {
 					labelSingular: collection.labelSingular || collection.label,
 					supports: collection.supports || [],
 					hasSeo: collection.hasSeo,
+					urlPattern: collection.urlPattern,
 					fields,
 				};
 			}