test(lsp): add hemplate highlighting fixture

Add repo-owned hemplate highlighting fixture and golden capture contract without editor packaging or a second parser.

req: diagnostics/004

req: diagnostics/008

hemx-lsp/src/main.rs

@@ -903,6 +903,44 @@ mod tests {
         assert!(value.contains("docs/hemplate-syntax.md"));
     }
 
+    #[test]
+    fn hemplate_highlighting_fixture_covers_documented_overlay_tokens() {
+        // req: diagnostics/004 req: diagnostics/008
+        let fixture = include_str!("../../docs/fixtures/hemplate-highlighting/hemplate.heml");
+        let captures = include_str!("../../docs/fixtures/hemplate-highlighting/captures.tsv");
+        let allowed_captures = [
+            "@attribute.hemx",
+            "@attribute.dynamic.hemplate",
+            "@keyword.control.hemplate",
+            "@punctuation.special.hemplate.escaped.open",
+            "@punctuation.special.hemplate.escaped.close",
+            "@punctuation.special.hemplate.trusted.open",
+            "@punctuation.special.hemplate.trusted.close",
+            "@embedded.rust.hemplate",
+        ]
+        .into_iter()
+        .collect::<std::collections::BTreeSet<_>>();
+        let mut seen = std::collections::BTreeSet::new();
+        for (index, line) in captures.lines().enumerate().skip(1) {
+            let (capture, literal) = line
+                .split_once('\t')
+                .unwrap_or_else(|| panic!("capture row {index} must be TSV"));
+            assert!(
+                allowed_captures.contains(capture),
+                "unexpected capture `{capture}` in row {index}"
+            );
+            assert!(
+                fixture.contains(literal),
+                "highlight fixture missing literal `{literal}` for capture `{capture}`"
+            );
+            seen.insert(capture);
+        }
+        assert_eq!(
+            seen, allowed_captures,
+            "highlight fixture should exercise every documented overlay capture class"
+        );
+    }
+
     #[test]
     fn workout_template_fields_are_available_from_repo_facts() {
         // req: diagnostics/006