bug(demo-android): PostEndpointType.Custom receives slug instead of restBase

Context

In PR #433 (feat/demo-edit-existing-posts), the Android demo app maps PostTypeDetails to PostEndpointType for REST API calls. The mapping for custom post types passes the wrong value.

Bug

In both EditorActivity.persistPost() and PostsListActivity.loadPosts(), the else branch passes postType.postType (the slug, e.g. "product") to PostEndpointType.Custom():

else -> PostEndpointType.Custom(configuration.postType.postType)  // slug: "product"

However, PostEndpointType.Custom expects a restBase value (e.g. "products"), which is used directly as a URL path segment (/wp/v2/<value>/<id>). This is confirmed by the wordpress-rs source where PostEndpointType::Custom uses strum Display to serialize the inner string verbatim into the URL path.

The iOS demo correctly passes restBase:

endpointType = .custom(configuration.postType.restBase)  // restBase: "products"

Impact

For any custom post type where slug ≠ restBase (the common case, e.g. slug "product" vs restBase "products"), Android will construct URLs like /wp/v2/product/123 instead of /wp/v2/products/123, resulting in rest_no_route errors on both save and list operations.

Fix

Change postType.postType to postType.restBase in both locations:

• EditorActivity.kt (~line 361)
• PostsListActivity.kt (~line 181)

Inspect the custom post type mapping in EditorActivity.kt around line 361 and PostsListActivity.kt around line 181. Compare the Android mapping with the iOS demo and verify that both save and list requests use restBase, producing the correct WordPress REST URL for custom post types.