Fix E2E test gaps and add comprehensive E2E + parity test suites

- Fix pull consumer fetch: send original stream subject in HMSG (not inbox)
  so NATS client distinguishes data messages from control messages
- Fix MaxAge expiry: add background timer in StreamManager for periodic pruning
- Fix JetStream wire format: Go-compatible anonymous objects with string enums,
  proper offset-based pagination for stream/consumer list APIs
- Add 42 E2E black-box tests (core messaging, auth, TLS, accounts, JetStream)
- Add ~1000 parity tests across all subsystems (gaps closure)
- Update gap inventory docs to reflect implementation status

tests/NATS.Server.Tests/NatsConfLexerTests.cs

@@ -83,6 +83,14 @@ public class NatsConfLexerTests
         keys[0].Value.ShouldBe("foo");
     }
 
+    [Fact]
+    public void Lex_CommentBody_EmitsTextToken()
+    {
+        var tokens = NatsConfLexer.Tokenize("# this is a comment\nfoo = 1").ToList();
+        var commentBody = tokens.Single(t => t.Type == TokenType.Text);
+        commentBody.Value.ShouldBe(" this is a comment");
+    }
+
     [Fact]
     public void Lex_SlashComment_IsIgnored()
     {
@@ -218,4 +226,13 @@ public class NatsConfLexerTests
         tokens[1].Type.ShouldBe(TokenType.String);
         tokens[1].Value.ShouldBe("3xyz");
     }
+
+    [Fact]
+    public void Lex_Unicode_surrogate_pairs_in_strings_are_preserved()
+    {
+        var tokens = NatsConfLexer.Tokenize("msg = \"rocket🚀\"\nport = 4222").ToList();
+        tokens[1].Type.ShouldBe(TokenType.String);
+        tokens[1].Value.ShouldBe("rocket🚀");
+        tokens[2].Line.ShouldBe(2);
+    }
 }