Fix Java test type mismatch: PingResult.timestamp is Long not String

The generated PingResult record has timestamp as Long (milliseconds),
but tests were passing String values (ISO date format). Update tests
to use Long millisecond values instead.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

java/src/test/java/com/github/copilot/sdk/generated/rpc/GeneratedRpcRecordsCoverageTest.java

@@ -32,9 +32,9 @@ void pingParams_record() {
 
     @Test
     void pingResult_record() {
-        var result = new PingResult("pong", "2026-01-01T00:00:00Z", 2L);
+        var result = new PingResult("pong", 1735689600000L, 2L);
         assertEquals("pong", result.message());
-        assertEquals("2026-01-01T00:00:00Z", result.timestamp());
+        assertEquals(1735689600000L, result.timestamp());
         assertEquals(2L, result.protocolVersion());
     }
 
@@ -471,9 +471,9 @@ void sessionWorkspaceReadFileParams_record() {
 
     @Test
     void pingResult_fields() {
-        var result = new PingResult("pong", "2026-06-15T10:30:00Z", 1L);
+        var result = new PingResult("pong", 1750000200000L, 1L);
         assertEquals("pong", result.message());
-        assertEquals("2026-06-15T10:30:00Z", result.timestamp());
+        assertEquals(1750000200000L, result.timestamp());
         assertEquals(1L, result.protocolVersion());
     }