Validate scoped filter registry

Reject scoped configurations whose filters registry is present but not an
object, so invalid user input fails with ConfigError instead of reaching
Object.values() with a primitive value.

#188 (comment)

Assisted-by: Codex:gpt-5.5

Author: dahlia

packages/logtape/src/config.test.ts

@@ -582,6 +582,15 @@ test("withConfig() rejects invalid scoped configuration", async () => {
         } as never, () => {}),
       ConfigError,
     );
+    await assert.rejects(
+      () =>
+        withConfig({
+          sinks: {},
+          filters: "filter",
+          loggers: [],
+        } as never, () => {}),
+      ConfigError,
+    );
     await assert.rejects(
       () =>
         withConfig({

packages/logtape/src/scoped-config.ts

@@ -77,6 +77,9 @@ export function compileScopedConfig<
   if (!Array.isArray(config.loggers)) {
     throw createError("Configuration must include a loggers array.");
   }
+  if (config.filters !== undefined && !isObjectLike(config.filters)) {
+    throw createError("Configuration filters must be an object.");
+  }
 
   const nodes = new Map<string, CompiledScopedLogger>();
   const configuredCategories = new Set<string>();