feat(kernel): RepoKnowledgeRetriever port + relevance-retrieved repo context with recency fallback

testing/kernel/src/test/kotlin/ContextFeedbackTest.kt

@@ -10,8 +10,10 @@ import com.correx.core.events.types.ArtifactId
 import com.correx.core.events.types.SessionId
 import com.correx.core.events.types.StageId
 import com.correx.core.events.types.TransitionId
+import com.correx.core.events.events.RepoKnowledgeHit
 import com.correx.core.kernel.orchestration.buildArtifactKindVocabularyEntry
 import com.correx.core.kernel.orchestration.buildProjectProfileEntry
+import com.correx.core.kernel.orchestration.buildRelevantFilesEntry
 import com.correx.core.kernel.orchestration.buildRetryFeedbackEntry
 import com.correx.core.kernel.orchestration.criticArtifactIds
 import com.correx.core.sessions.BoundProjectProfile
@@ -109,6 +111,20 @@ class ContextFeedbackTest {
         assertTrue(entry.content.contains("report (llm-emitted)"), "content should flag llm-emitted: ${entry.content}")
     }
 
+    @Test
+    fun `buildRelevantFilesEntry produces L3 system entry with Relevant files header`() {
+        val hits = listOf(
+            RepoKnowledgeHit(path = "src/Parser.kt", text = "src/Parser.kt: Parser, Lexer", score = 0.9f),
+            RepoKnowledgeHit(path = "src/Main.kt", text = "src/Main.kt: main", score = 0.7f),
+        )
+        val entry = buildRelevantFilesEntry(hits)
+        assertEquals(ContextLayer.L3, entry.layer)
+        assertEquals(EntryRole.SYSTEM, entry.role)
+        assertEquals("relevantFiles", entry.sourceType)
+        assertTrue(entry.content.startsWith("## Relevant files"), "content: ${entry.content}")
+        assertTrue(entry.content.contains("src/Parser.kt"), "content: ${entry.content}")
+    }
+
     @Test
     fun `no refinement events yields empty set`() {
         assertTrue(criticArtifactIds(emptyList(), graphWith(), StageId("implement")).isEmpty())