feat(plugin): add Tags field to ModPlugin

TDD approach: added failing tests in mod_test.go that check parsing and
null-coalescing of tags, then added the []string Tags field to ModPlugin
struct with TOML tag "tags,omitempty".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

plugin/mod.go

@@ -32,6 +32,7 @@ type ModPlugin struct {
 	Version    string   `toml:"version"`
 	Kind       string   `toml:"kind,omitempty"`
 	Categories []string `toml:"categories,omitempty"`
+	Tags       []string `toml:"tags,omitempty"`
 	// RequiredIconPacks names icon-pack slugs the host CMS must ensure are
 	// installed before the plugin is loaded (e.g. "tabler", "phosphor"). The
 	// standalone-plugin loader honours this best-effort by auto-installing any

plugin/mod_test.go

@@ -365,3 +365,39 @@ func TestNormalizeTags_NilInput(t *testing.T) {
 		t.Errorf("got %v, want empty", got)
 	}
 }
+
+func TestParseModFull_Tags(t *testing.T) {
+	src := []byte(`
+[plugin]
+name = "dark-pro"
+scope = "themes"
+version = "0.1.0"
+kind = "theme"
+tags = ["dark", "agency", "serif"]
+`)
+	m, err := ParseModFull(src)
+	if err != nil {
+		t.Fatalf("ParseModFull err: %v", err)
+	}
+	if len(m.Plugin.Tags) != 3 {
+		t.Fatalf("Tags len = %d, want 3 (%v)", len(m.Plugin.Tags), m.Plugin.Tags)
+	}
+	if m.Plugin.Tags[0] != "dark" || m.Plugin.Tags[1] != "agency" || m.Plugin.Tags[2] != "serif" {
+		t.Errorf("Tags = %v", m.Plugin.Tags)
+	}
+}
+
+func TestParseModFull_TagsOmittedIsNil(t *testing.T) {
+	src := []byte(`
+[plugin]
+name = "no-tags"
+version = "0.1.0"
+`)
+	m, err := ParseModFull(src)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if m.Plugin.Tags != nil {
+		t.Errorf("Tags = %v, want nil when omitted", m.Plugin.Tags)
+	}
+}