fix: isWebBricksBackendResource() must extract path from full URLs before matching /public

Bug: when fetchUi('/public') resolves to http://host:port/public, the
isWebBricksBackendResource() check compared the full URL string against
'/public' and always returned false, so _webbricks_=1 was never added.

Fix: extract the path component from full URLs (strip scheme+host) before
running the .ui/.dspy/public/root detection logic. All HTTP methods
(getText/getJson/postJson/postForm) delegate to withBackendContextIfNeeded
which calls isWebBricksBackendResource, so this fix covers all code paths.

shared/src/commonMain/kotlin/com/bricks/mp/core/WebBricksRequestContext.kt

@@ -54,9 +54,21 @@ fun withWebBricksRequestContext(
  * Detect URLs that need WebBricks backend context (_webbricks_=1).
  * Covers both direct .ui/.dspy paths and index fallback paths that the
  * server resolves to .ui files (e.g. "/" → index.ui, "/public" → index.ui).
+ *
+ * Handles both full URLs (http://host:port/public) and path-only strings (/public).
  */
 fun String.isWebBricksBackendResource(): Boolean {
-    val path = substringBefore('?').substringBefore('#')
+    val withoutQuery = substringBefore('?').substringBefore('#')
+
+    // Extract path component: strip scheme+host for full URLs, keep as-is for paths
+    val path = if (withoutQuery.contains("://")) {
+        // Full URL: find first '/' after "://"
+        val afterScheme = withoutQuery.substringAfter("://")
+        "/" + afterScheme.substringAfter('/', missingDelimiterValue = "")
+    } else {
+        withoutQuery
+    }
+
     val normalized = path.trimEnd('/')
 
     // Direct .ui/.dspy resource