Add GUI parity for -c/-a, mDNS/SSH dissectors, and two new fuzz harnesses

GUI parity: checksum_status()/reassembled_http_status() moved out of
main.cpp into a shared wireframe/packet_diagnostics.hpp so the GUI can
show the same -c/-a diagnostics for the selected packet without
duplicating the Ethernet/IPv4/TCP walk. Visually verified under Xvfb
with the same split-segment scenario used to verify -a on the CLI.

Two new L7 dissectors: mDNS (reuses parse_dns outright - RFC 6762
keeps DNS's wire format, just a different port) and SSH's cleartext
identification banner. Live-verified against this machine's real
sshd and a real DNS-wire-format packet sent to port 5353.

Two new fuzz harnesses (fuzz_checksum, fuzz_tcp_reassembly) covering
code added here that the original nine harnesses never
touched. All 12 run clean across ~90M executions with no crashes.

NAMES.md and PLAN.md updated with this round's decisions and naming
candidates.

1 files changed, 60 insertions, 0 deletions

diff --git a/tests/test_mdns.cpp b/tests/test_mdns.cpp
new file mode 100644
index 0000000..cad77e7
--- /dev/null
+++ b/tests/test_mdns.cpp
@@ -0,0 +1,60 @@
+#include <doctest/doctest.h>
+
+#include <vector>
+
+#include "wireframe/l7/mdns.hpp"
+
+using namespace wireframe::net;
+
+namespace {
+
+// A typical mDNS query for a ".local" hostname, id=0 per RFC 6762
+// 18.1's convention for multicast queries.
+std::vector<unsigned char> mdns_query() {
+    return {
+        0x00, 0x00,  // id = 0
+        0x00, 0x00,  // flags: query
+        0x00, 0x01,  // qdcount = 1
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        6, 'm', 'y', 'h', 'o', 's', 't', 5, 'l', 'o', 'c', 'a', 'l', 0,
+        0x00, 0x01,  // qtype = A
+        0x00, 0x01,  // qclass = IN
+    };
+}
+
+}  // namespace
+
+TEST_CASE("MdnsDissector claims port 5353") {
+    MdnsDissector dissector;
+    CHECK(dissector.port() == kMdnsPort);
+}
+
+TEST_CASE("MdnsDissector summarizes a query without an id= field") {
+    MdnsDissector dissector;
+    auto summary = dissector.summarize(mdns_query());
+    REQUIRE(summary.has_value());
+    CHECK(summary->substr(0, 10) == "mDNS query");
+    CHECK(summary->find("myhost.local") != std::string::npos);
+    CHECK(summary->find("id=") == std::string::npos);
+}
+
+TEST_CASE("MdnsDissector summarizes a response with ancount") {
+    MdnsDissector dissector;
+    std::vector<unsigned char> bytes = {
+        0x00, 0x00,
+        0x84, 0x00,  // flags: QR=1 (response), AA=1
+        0x00, 0x00,  // qdcount = 0 (typical for an mDNS response)
+        0x00, 0x01,  // ancount = 1
+        0x00, 0x00, 0x00, 0x00,
+    };
+    auto summary = dissector.summarize(bytes);
+    REQUIRE(summary.has_value());
+    CHECK(summary->substr(0, 13) == "mDNS response");
+    CHECK(summary->find("ancount=1") != std::string::npos);
+}
+
+TEST_CASE("MdnsDissector::summarize returns nullopt for a truncated payload") {
+    MdnsDissector dissector;
+    std::vector<unsigned char> bytes(5, 0);
+    CHECK_FALSE(dissector.summarize(bytes).has_value());
+}