test(rust-lsp): tag the shared-registry fixtures as Rust defs

The shared Tier-2 build now registers Rust definitions only. Two
fixtures that feed cbm_rust_build_cross_registry left CBMLSPDef.lang
zero, which the pipeline never does (pass_lsp_cross.c tags every def
with its file's language). The other shared-registry fixtures in this
file already set CBM_LANG_RUST. Set it on these two as well.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

tests/test_rust_lsp.c

@@ -591,6 +591,9 @@ TEST(rustlsp_shared_registry_resolves_like_per_file) {
     defs[1].receiver_type = "test.demo.Database";
     defs[1].def_module_qn = "test.demo";
     defs[1].return_types = "alloc.string.String";
+    /* The shared build registers Rust defs only, as the pipeline tags them. */
+    defs[0].lang = CBM_LANG_RUST;
+    defs[1].lang = CBM_LANG_RUST;
 
     const char *imp_names[] = {"demo"};
     const char *imp_qns[] = {"test::demo"};
@@ -695,6 +698,7 @@ TEST(rustlsp_shared_registry_macro_hidden_call_has_carrier) {
     defs[0].label = "Function";
     defs[0].def_module_qn = "test.lib";
     defs[0].return_types = "str";
+    defs[0].lang = CBM_LANG_RUST;
 
     const char *imp_names[] = {"lib"};
     const char *imp_qns[] = {"test::lib"};