Integrate with herdr cli.

build.zig

@@ -180,6 +180,18 @@ pub fn build(b: *std.Build) void {
     palette_tests.root_module.addImport("ghostty-vt", ghostty.module("ghostty-vt"));
     test_step.dependOn(&b.addRunArtifact(palette_tests).step);
 
+    // herdr-core's frame format is its own root: the bytes of the wire
+    // protocol, testable with no core to talk to. The connection on top of it
+    // wants a socket and a main loop, and is checked by running it.
+    const hc_frame_tests = b.addTest(.{
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/hc/frame.zig"),
+            .target = target,
+            .optimize = optimize,
+        }),
+    });
+    test_step.dependOn(&b.addRunArtifact(hc_frame_tests).step);
+
     // And a root for the settings file itself. `Settings.zig` reaches GLib for
     // where the file lives, but reading and writing its *contents* is pure
     // enough to test — which is what these cover, since the palette overrides