fix(ext): update stale HeaderMap references to Http1HeaderMap

HeaderMap was split into the HeaderView interface and Http1HeaderMap
impl in the HTTP/2 model refactor, but two extension-module tests
(flash-ext-jackson, flash-ext-view-jte) still referenced the old
class name, breaking the CI build on master after the HTTP/2 PR merge.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JCmqb7XGb3JQvCWf589yma

flash-extensions/flash-ext-jackson/src/test/java/dev/relism/flash/ext/jackson/JsonTest.java

@@ -5,7 +5,7 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import dev.relism.flash.exceptions.HttpException;
 import dev.relism.flash.http.ContentType;
 import dev.relism.flash.http.HttpMethod;
-import dev.relism.flash.models.HeaderMap;
+import dev.relism.flash.models.Http1HeaderMap;
 import dev.relism.flash.models.Request;
 import dev.relism.flash.models.RequestLine;
 import dev.relism.flash.models.Response;
@@ -82,7 +82,7 @@ class JsonTest {
                 new FastPathViews.StringByteView("/json"),
                 null,
                 new FastPathViews.StringByteView("HTTP/1.1"),
-                new HeaderMap()
+                new Http1HeaderMap()
         );
         return new Request(line, body);
     }

flash-extensions/flash-ext-view-jte/src/test/java/dev/relism/flash/ext/view/jte/JteExtensionTest.java

@@ -148,7 +148,7 @@ class JteExtensionTest {
     }
 
     private static Request request(String path, String query, String acceptEncoding, String origin) {
-        dev.relism.flash.models.HeaderMap headers = new dev.relism.flash.models.HeaderMap();
+        dev.relism.flash.models.Http1HeaderMap headers = new dev.relism.flash.models.Http1HeaderMap();
         String raw = "Host: localhost\r\n";
         if (acceptEncoding != null) raw += "Accept-Encoding: " + acceptEncoding + "\r\n";
         if (origin != null) raw += "Origin: " + origin + "\r\n";