fix(discover): map .NET XML files (#6)

## Summary
- Recognize .NET project, resource, XAML, and manifest extensions as XML during discovery.
- Adapt upstream XML discovery commit `e0becdeb`.

## Provenance and gates
- Agent Run: `luna-cbm-xml-20260920`; source revision `a43b2201`; worker commit `d6177b61`.
- Agent-Workflow reports a valid completion receipt. Independent review, evaluation, acceptance, and integration are pending.
- `git diff --check main...HEAD` passed. No tests were run for this PR request.



Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: ngallodev

src/discover/language.c

@@ -312,6 +312,25 @@ static const ext_entry_t EXT_TABLE[] = {
     {".xsd", CBM_LANG_XML},
     {".xsl", CBM_LANG_XML},
     {".svg", CBM_LANG_XML},
+    /* MSBuild project system. */
+    {".csproj", CBM_LANG_XML},
+    {".vbproj", CBM_LANG_XML},
+    {".fsproj", CBM_LANG_XML},
+    {".props", CBM_LANG_XML},
+    {".targets", CBM_LANG_XML},
+    {".nuspec", CBM_LANG_XML},
+    {".slnx", CBM_LANG_XML},
+    {".runsettings", CBM_LANG_XML},
+    /* .NET resource files. */
+    {".resx", CBM_LANG_XML},
+    /* XAML views. */
+    {".xaml", CBM_LANG_XML},
+    {".axaml", CBM_LANG_XML},
+    /* Application manifests. */
+    {".plist", CBM_LANG_XML},
+    {".xcprivacy", CBM_LANG_XML},
+    {".manifest", CBM_LANG_XML},
+    {".appxmanifest", CBM_LANG_XML},
 
     /* YAML */
     {".yaml", CBM_LANG_YAML},

tests/test_language.c

@@ -404,6 +404,33 @@ TEST(lang_ext_svg) {
     ASSERT_EQ(cbm_language_for_extension(".svg"), CBM_LANG_XML);
     PASS();
 }
+TEST(lang_ext_msbuild_projects) {
+    ASSERT_EQ(cbm_language_for_extension(".csproj"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".vbproj"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".fsproj"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".props"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".targets"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".nuspec"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".slnx"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".runsettings"), CBM_LANG_XML);
+    PASS();
+}
+TEST(lang_ext_resx) {
+    ASSERT_EQ(cbm_language_for_extension(".resx"), CBM_LANG_XML);
+    PASS();
+}
+TEST(lang_ext_xaml) {
+    ASSERT_EQ(cbm_language_for_extension(".xaml"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".axaml"), CBM_LANG_XML);
+    PASS();
+}
+TEST(lang_ext_app_manifests) {
+    ASSERT_EQ(cbm_language_for_extension(".plist"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".xcprivacy"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".manifest"), CBM_LANG_XML);
+    ASSERT_EQ(cbm_language_for_extension(".appxmanifest"), CBM_LANG_XML);
+    PASS();
+}
 TEST(lang_ext_markdown) {
     ASSERT_EQ(cbm_language_for_extension(".md"), CBM_LANG_MARKDOWN);
     PASS();
@@ -1351,6 +1378,10 @@ SUITE(language) {
     RUN_TEST(lang_ext_xsl);
     RUN_TEST(lang_ext_xsd);
     RUN_TEST(lang_ext_svg);
+    RUN_TEST(lang_ext_msbuild_projects);
+    RUN_TEST(lang_ext_resx);
+    RUN_TEST(lang_ext_xaml);
+    RUN_TEST(lang_ext_app_manifests);
     RUN_TEST(lang_ext_markdown);
     RUN_TEST(lang_ext_mdx);
     RUN_TEST(lang_ext_makefile);