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.

apps/tui/src/main/kotlin/com/correx/apps/tui/components/ActiveSession.kt

@@ -16,6 +16,11 @@ fun activeSessionWidget(session: SessionSummary?): Paragraph {
         val lines = buildList<Line> {
             add(Line.from(Span.raw("stage: ${session.currentStage ?: "—"}")))
             session.lastOutput?.let { add(Line.from(Span.raw("last output: $it"))) }
+            session.lastResponseText?.takeIf { it.isNotEmpty() }?.let { text ->
+                add(Line.from(Span.raw("")))
+                add(Line.from(Span.raw("response:")))
+                text.lineSequence().forEach { add(Line.from(Span.raw(it))) }
+            }
         }
         Text.from(lines)
     }

apps/tui/src/main/kotlin/com/correx/apps/tui/reducer/SessionsReducer.kt

@@ -100,15 +100,7 @@ object SessionsReducer {
         )
         is ServerMessage.StageCompleted -> touchSession(sessions, msg.sessionId.value, null, clock)
         is ServerMessage.StageFailed -> touchSession(sessions, msg.sessionId.value, null, clock)
-        is ServerMessage.InferenceCompleted -> sessions.copy(
-            sessions = sessions.sessions.map { s ->
-                if (s.id == msg.sessionId.value) {
-                    s.copy(lastOutput = msg.outputSummary, lastEventAt = clock())
-                } else {
-                    s
-                }
-            },
-        )
+        is ServerMessage.InferenceCompleted -> applyInferenceCompleted(sessions, msg, clock)
         is ServerMessage.ToolCompleted -> sessions.copy(
             sessions = sessions.sessions.map { s ->
                 if (s.id == msg.sessionId.value) {
@@ -121,6 +113,24 @@ object SessionsReducer {
         else -> sessions
     }
 
+    private fun applyInferenceCompleted(
+        sessions: SessionsState,
+        msg: ServerMessage.InferenceCompleted,
+        clock: () -> Long,
+    ): SessionsState = sessions.copy(
+        sessions = sessions.sessions.map { s ->
+            if (s.id == msg.sessionId.value) {
+                s.copy(
+                    lastOutput = msg.outputSummary,
+                    lastResponseText = msg.responseText.takeIf { it.isNotEmpty() },
+                    lastEventAt = clock(),
+                )
+            } else {
+                s
+            }
+        },
+    )
+
     private fun touchSession(
         sessions: SessionsState,
         sessionId: String,

apps/tui/src/main/kotlin/com/correx/apps/tui/state/TuiState.kt

@@ -17,6 +17,7 @@ data class SessionSummary(
     val lastEventAt: Long,
     val currentStage: String?,
     val lastOutput: String?,
+    val lastResponseText: String? = null,
 )
 
 data class ApprovalInfo(