feat: persist and transfer script command payloads

internal/client/spool/script.go

@@ -102,7 +102,7 @@ func (store *Store) AppendScriptChunk(ctx context.Context, issueUUID domain.UUID
 	if err != nil {
 		return ScriptStatus{}, err
 	}
-	if row.Committed {
+	if row.Committed && offset >= row.ReceivedBytes {
 		return ScriptStatus{}, ErrScriptTerminal
 	}
 	if offset > row.ReceivedBytes {
@@ -123,8 +123,17 @@ func (store *Store) AppendScriptChunk(ctx context.Context, issueUUID domain.UUID
 		if end > row.ReceivedBytes || !bytes.Equal(raw[offset:end], data) {
 			return ScriptStatus{}, ErrScriptOverlap
 		}
+		// A reconnect can replay a chunk after the client has already committed
+		// the complete script. Exact byte-for-byte replays are safe and must be
+		// idempotent; a new byte after commit remains forbidden.
+		if row.Committed {
+			return ScriptStatus{ReceivedBytes: row.ReceivedBytes, Committed: true, Duplicate: true}, tx.Commit()
+		}
 		return ScriptStatus{ReceivedBytes: row.ReceivedBytes, Duplicate: true}, tx.Commit()
 	}
+	if row.Committed {
+		return ScriptStatus{}, ErrScriptTerminal
+	}
 	updatedRaw := append(raw, data...)
 	stored, err := compressScript(updatedRaw)
 	if err != nil {

internal/client/spool/script_test.go

@@ -63,6 +63,10 @@ func TestScriptUploadDurableExactReplayAndCommit_HP_SCRIPT_01(t *testing.T) {
 	if err != nil || !duplicate.Duplicate || !duplicate.Committed {
 		t.Fatalf("ScriptCommit replay = %#v, %v", duplicate, err)
 	}
+	duplicate, err = store.AppendScriptChunk(ctx, issue, 0, raw[:len(first)], sha256.Sum256(raw[:len(first)]))
+	if err != nil || !duplicate.Duplicate || !duplicate.Committed || duplicate.ReceivedBytes != uint64(len(raw)) {
+		t.Fatalf("post-commit ScriptChunk replay = %#v, %v", duplicate, err)
+	}
 	if _, err := store.AppendScriptChunk(ctx, issue, uint64(len(raw)), []byte("!"), sha256.Sum256([]byte("!"))); !errors.Is(err, ErrScriptTerminal) {
 		t.Fatalf("post-commit chunk error = %v, want ErrScriptTerminal", err)
 	}