fix(memory): turnId repoRoot prefix collision (/repo vs /repo2)

The repo-map turnId tag and the L3 retriever filter used 'repomap:$repoRoot' with no
delimiter, so a retriever for /repo also matched /repo2 entries (startsWith). Add a trailing
':' to the tag (no-stateKey branch) and the retriever filter so the repoRoot boundary is
explicit. Test: /repo retrieval no longer leaks /repo2 entries, still matches its own
with/without a stateKey suffix.

apps/server/src/main/kotlin/com/correx/apps/server/memory/L3RepoKnowledgeRetriever.kt

@@ -17,7 +17,8 @@ class L3RepoKnowledgeRetriever(
     override suspend fun retrieve(sessionId: SessionId, query: String, k: Int): List<RepoKnowledgeHit> {
         val vector = embedder.embed(query)
         return l3MemoryStore.query(L3Query(vector = vector, k = k * RETRIEVAL_OVERSAMPLE_FACTOR))
-            .filter { it.entry.turnId.startsWith("repomap:$repoRoot") }
+            // Trailing ':' so "/repo" does not also match "/repo2" turnIds (prefix collision).
+            .filter { it.entry.turnId.startsWith("repomap:$repoRoot:") }
             .take(k)
             .map { RepoKnowledgeHit(path = it.entry.text.substringBefore(":"), text = it.entry.text, score = it.score) }
     }

apps/server/src/main/kotlin/com/correx/apps/server/memory/ProjectMemoryService.kt

@@ -85,7 +85,9 @@ class ProjectMemoryService(
                     ),
                 ),
             )
-            val tag = if (stateKey != null) "repomap:$repoRoot:$stateKey" else "repomap:$repoRoot"
+            // Trailing ':' delimiter so a repoRoot prefix can't collide with a longer sibling
+            // (/repo vs /repo2) under the retriever's startsWith filter.
+            val tag = if (stateKey != null) "repomap:$repoRoot:$stateKey" else "repomap:$repoRoot:"
             entries.forEach { entry ->
                 runCatching {
                     val text = entry.path + if (entry.symbols.isEmpty()) "" else ": ${entry.symbols.joinToString(", ")}"

apps/server/src/test/kotlin/com/correx/apps/server/memory/L3RepoKnowledgeRetrieverTest.kt

@@ -0,0 +1,42 @@
+package com.correx.apps.server.memory
+
+import com.correx.core.events.types.SessionId
+import com.correx.core.inference.Embedder
+import com.correx.core.router.l3.InMemoryL3MemoryStore
+import com.correx.core.router.l3.L3MemoryEntry
+import kotlinx.coroutines.runBlocking
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+private class RetrieverConstantEmbedder(override val dimension: Int = 4) : Embedder {
+    override suspend fun embed(text: String): FloatArray = FloatArray(dimension) { 0.5f }
+}
+
+class L3RepoKnowledgeRetrieverTest {
+
+    private val vec = FloatArray(4) { 0.5f }
+
+    @Test
+    fun `retriever for a repoRoot does not match a sibling whose path it prefixes`(): Unit = runBlocking {
+        val l3 = InMemoryL3MemoryStore()
+        l3.store(L3MemoryEntry("1", SessionId("s"), "repomap:/repo:git:h", "repo/A.kt: Foo", vec, 0L))
+        l3.store(L3MemoryEntry("2", SessionId("s"), "repomap:/repo2:git:h", "repo2/B.kt: Bar", vec, 0L))
+
+        val hits = L3RepoKnowledgeRetriever(RetrieverConstantEmbedder(), l3, "/repo")
+            .retrieve(SessionId("s"), "anything", 10)
+
+        assertEquals(listOf("repo/A.kt: Foo"), hits.map { it.text }, "must not leak /repo2 entries into /repo")
+    }
+
+    @Test
+    fun `retriever matches its own repoRoot entries with or without a stateKey suffix`(): Unit = runBlocking {
+        val l3 = InMemoryL3MemoryStore()
+        l3.store(L3MemoryEntry("1", SessionId("s"), "repomap:/repo:git:h1", "repo/A.kt", vec, 0L))
+        l3.store(L3MemoryEntry("2", SessionId("s"), "repomap:/repo:", "repo/B.kt", vec, 0L))
+
+        val hits = L3RepoKnowledgeRetriever(RetrieverConstantEmbedder(), l3, "/repo")
+            .retrieve(SessionId("s"), "anything", 10)
+
+        assertEquals(setOf("repo/A.kt", "repo/B.kt"), hits.map { it.text }.toSet())
+    }
+}