Add count methods to JournalStore API and implementations for message counting per conversation (count(conversationId) and count(conversationId, after)), with supporting tests.

journal-inmemory/src/commonMain/kotlin/pw/binom/agentik/journal/inmemory/InMemoryJournalStore.kt

@@ -59,6 +59,14 @@ class InMemoryJournalStore : MutableJournalStore {
         records.removeAll { it.conversationId == conversationId }
     }
 
+    override suspend fun count(conversationId: String): Long = mutex.withLock {
+        records.count { it.conversationId == conversationId }.toLong()
+    }
+
+    override suspend fun count(conversationId: String, after: Instant): Long = mutex.withLock {
+        records.count { it.conversationId == conversationId && it.createdAt > after }.toLong()
+    }
+
     /** Сколько записей сейчас в кэше. Для тестов/диагностики. */
     suspend fun size(): Int = mutex.withLock { records.size }
 

journal-inmemory/src/commonTest/kotlin/pw/binom/agentik/journal/inmemory/InMemoryJournalStoreTest.kt

@@ -77,4 +77,85 @@ class InMemoryJournalStoreTest {
         assertTrue(store.list("c1", Instant.DISTANT_PAST, 0, 100).isEmpty())
         assertEquals(listOf("m2"), store.list("c2", Instant.DISTANT_PAST, 0, 100).map { it.id })
     }
+
+    @Test
+    fun `count returns total per conversation`() = runTest {
+        val store = InMemoryJournalStore()
+        val t0 = Instant.parse("2026-09-21T10:00:00Z")
+        assertEquals(0L, store.count("c1"))
+
+        store.append(userMsg("m1", "c1", "a", t0))
+        store.append(userMsg("m2", "c1", "b", t0 + 1.seconds))
+        store.append(userMsg("m3", "c2", "c", t0 + 2.seconds))
+
+        assertEquals(2L, store.count("c1"))
+        assertEquals(1L, store.count("c2"))
+        assertEquals(0L, store.count("never-existed"))
+    }
+
+    @Test
+    fun `count is unaffected by clear of another conversation`() = runTest {
+        val store = InMemoryJournalStore()
+        val t0 = Instant.parse("2026-09-21T10:00:00Z")
+        for (i in 1..20) {
+            store.append(userMsg("m$i", "c1", "x", t0 + i.seconds))
+        }
+        store.append(userMsg("n1", "c2", "y", t0))
+        assertEquals(20L, store.count("c1"))
+        assertEquals(1L, store.count("c2"))
+
+        store.clear("c1")
+        assertEquals(0L, store.count("c1"))
+        assertEquals(1L, store.count("c2"))
+    }
+
+    @Test
+    fun `count after cursor excludes earlier messages`() = runTest {
+        val store = InMemoryJournalStore()
+        val t0 = Instant.parse("2026-09-21T10:00:00Z")
+        store.append(userMsg("m1", "c1", "a", t0))
+        store.append(userMsg("m2", "c1", "b", t0 + 10.seconds))
+        store.append(userMsg("m3", "c1", "c", t0 + 20.seconds))
+
+        // strictly > t0
+        assertEquals(2L, store.count("c1", t0))
+        // strictly > t0+10s — only the last
+        assertEquals(1L, store.count("c1", t0 + 10.seconds))
+        // after last — empty
+        assertEquals(0L, store.count("c1", t0 + 20.seconds))
+        // distant past — all
+        assertEquals(3L, store.count("c1", Instant.DISTANT_PAST))
+    }
+
+    @Test
+    fun `count after cursor scopes to conversation`() = runTest {
+        val store = InMemoryJournalStore()
+        val t = Instant.parse("2026-09-21T10:00:00Z")
+        store.append(userMsg("m1", "c1", "a", t))
+        store.append(userMsg("m2", "c2", "b", t))
+
+        val future = Instant.parse("2099-01-01T00:00:00Z")
+        assertEquals(0L, store.count("c1", future))
+        assertEquals(0L, store.count("c2", future))
+        assertEquals(1L, store.count("c1", Instant.DISTANT_PAST))
+        assertEquals(1L, store.count("c2", Instant.DISTANT_PAST))
+    }
+
+    @Test
+    fun `count agrees with list size`() = runTest {
+        val store = InMemoryJournalStore()
+        val t0 = Instant.parse("2026-09-21T10:00:00Z")
+        for (i in 1..15) {
+            store.append(userMsg("m$i", "c1", "x", t0 + i.seconds))
+        }
+        assertEquals(
+            store.list("c1", Instant.DISTANT_PAST, 0, 1000).size.toLong(),
+            store.count("c1"),
+        )
+        val cutoff = t0 + 7.seconds
+        assertEquals(
+            store.list("c1", cutoff, 0, 1000).size.toLong(),
+            store.count("c1", cutoff),
+        )
+    }
 }