feat(cas): content-addressed artifact store (steps 1–8)

New core:artifacts-store interface + infrastructure/artifacts-cas
implementation: segment files + SQLite index, Blake3 hashing,
group-commit fsync via flushBefore, recovery tail-scan, manual
compactor, and oldest-first disk-cap evictor.

Inference events now carry promptArtifactId / responseArtifactId;
orchestrators put bytes before emitting. SqliteEventStore wraps
its txn in artifactStore.flushBefore so segment data is fsynced
before the event commit, making the crash window non-corrupting
(TailScanner re-indexes orphan tail records on reopen).

Compactor and evictor are mutually exclusive via maintenanceMutex.
Step 9 (cloud sync) deferred to a later epic.

See docs/reviews/2026-05-18-cas-steps-1-8-review.md for the final
review.

testing/deterministic/src/test/kotlin/SessionReplayDeterminismTest.kt

@@ -11,6 +11,7 @@ import com.correx.core.sessions.DefaultSessionReducer
 import com.correx.core.sessions.SessionProjector
 import com.correx.core.sessions.projections.replay.DefaultEventReplayer
 import com.correx.infrastructure.persistence.InMemoryEventStore
+import kotlinx.coroutines.runBlocking
 import kotlinx.datetime.Clock
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Test
@@ -23,7 +24,7 @@ class SessionReplayDeterminismTest {
     )
 
     @Test
-    fun `same events produce same state`() {
+    fun `same events produce same state`(): Unit = runBlocking {
         val sessionId = SessionId("s1")
 
         val store1 = InMemoryEventStore()