feat: treat l0 retrieval as domain hint

src/test/java/com/superbiz/agent/service/KnowledgeIndexServiceTest.java

@@ -98,6 +98,46 @@ class KnowledgeIndexServiceTest {
         assertEquals(2, results.size());
     }
 
+    @Test
+    void testAnalyzeQuery_returnsStructuredHint() {
+        KnowledgeEntry entry = KnowledgeEntry.builder()
+                .filePath("mysql.md")
+                .title("MySQL Doc")
+                .keywords(List.of("mysql", "connection pool"))
+                .category("database")
+                .build();
+
+        service.addToIndex(entry);
+
+        KnowledgeIndexService.L0Hint hint = service.analyzeQuery("mysql connection pool timeout");
+
+        assertEquals(1, hint.matches().size());
+        assertEquals(List.of("mysql", "connection pool"), hint.matchedKeywords());
+        assertEquals(List.of("database"), hint.domains());
+        assertEquals(List.of("mysql", "connection pool"), hint.entities());
+        assertEquals(List.of("MySQL Doc"), hint.titles());
+        assertEquals("database", hint.singleDomainOrNull());
+    }
+
+    @Test
+    void testAnalyzeQuery_multipleDomainsHasNoSingleDomain() {
+        service.addToIndex(KnowledgeEntry.builder()
+                .filePath("mysql.md")
+                .keywords(List.of("timeout"))
+                .category("database")
+                .build());
+        service.addToIndex(KnowledgeEntry.builder()
+                .filePath("api.md")
+                .keywords(List.of("timeout"))
+                .category("api")
+                .build());
+
+        KnowledgeIndexService.L0Hint hint = service.analyzeQuery("timeout");
+
+        assertEquals(2, hint.matches().size());
+        assertNull(hint.singleDomainOrNull());
+    }
+
     @Test
     void testExactMatch_noMatch() {
         KnowledgeEntry entry = KnowledgeEntry.builder()

src/test/java/com/superbiz/agent/service/ToolInvocationRecorderTest.java

@@ -75,6 +75,9 @@ class ToolInvocationRecorderTest {
                 .success(true)
                 .evidenceStatus(ToolInvocationRecorder.EVIDENCE_STATUS_DEDUPED)
                 .l0Titles(List.of("payment/errors.md"))
+                .l0MatchedKeywords(List.of("ERR_TIMEOUT"))
+                .l0Domains(List.of("payment"))
+                .l0Entities(List.of("ERR_TIMEOUT"))
                 .build();
 
         try {
@@ -92,5 +95,8 @@ class ToolInvocationRecorderTest {
         assertEquals("doc_retrieved", saved.getDedupReason());
         assertTrue(saved.getRetrievalDetails().contains("\"evidence_status\":\"deduped\""));
         assertTrue(saved.getRetrievalDetails().contains("\"retrieved_domains\":[\"payment\"]"));
+        assertTrue(saved.getRetrievalDetails().contains("\"l0_matched_keywords\":[\"ERR_TIMEOUT\"]"));
+        assertTrue(saved.getRetrievalDetails().contains("\"l0_domains\":[\"payment\"]"));
+        assertTrue(saved.getRetrievalDetails().contains("\"l0_entities\":[\"ERR_TIMEOUT\"]"));
     }
 }