Add Seriatim trim adapter support

internal/adapters/seriatim/fake_test.go

@@ -51,3 +51,51 @@ func TestFakeRunnerError(t *testing.T) {
 		t.Fatal("expected error, got nil")
 	}
 }
+
+func TestFakeRunnerTrimCapturesRequestAndReturnsPath(t *testing.T) {
+	fake := &FakeRunner{}
+	dir := t.TempDir()
+	req := TrimRequest{
+		GeneratedConfigPath: filepath.Join(dir, "config", "seriatim.trim.yml"),
+		InputTranscriptPath: filepath.Join(dir, "transcripts", "processed.json"),
+		OutputTrimmedPath:   filepath.Join(dir, "transcripts", "trimmed.json"),
+		KeepSelector:        "1-10",
+		StdoutLogPath:       filepath.Join(dir, "logs", "seriatim.trim.stdout.log"),
+		StderrLogPath:       filepath.Join(dir, "logs", "seriatim.trim.stderr.log"),
+	}
+
+	res, err := fake.Trim(context.Background(), req)
+	if err != nil {
+		t.Fatalf("Trim() error = %v", err)
+	}
+	if len(fake.TrimRequests) != 1 || fake.TrimRequests[0].GeneratedConfigPath == "" {
+		t.Fatalf("trim requests = %#v, want captured request", fake.TrimRequests)
+	}
+	if res.OutputTrimmedPath != req.OutputTrimmedPath {
+		t.Fatalf("trimmed path = %q, want %q", res.OutputTrimmedPath, req.OutputTrimmedPath)
+	}
+	if res.KeepSelector != req.KeepSelector {
+		t.Fatalf("keep selector = %q, want %q", res.KeepSelector, req.KeepSelector)
+	}
+
+	cfgData, err := os.ReadFile(req.GeneratedConfigPath)
+	if err != nil {
+		t.Fatalf("read generated config: %v", err)
+	}
+	if !strings.Contains(string(cfgData), "command: trim") {
+		t.Fatalf("generated config = %q, want trim command marker", string(cfgData))
+	}
+	for _, logPath := range []string{req.StdoutLogPath, req.StderrLogPath} {
+		if _, err := os.Stat(logPath); err != nil {
+			t.Fatalf("expected log file %q to exist: %v", logPath, err)
+		}
+	}
+}
+
+func TestFakeRunnerTrimError(t *testing.T) {
+	fake := &FakeRunner{TrimErr: errors.New("boom")}
+	_, err := fake.Trim(context.Background(), TrimRequest{})
+	if err == nil {
+		t.Fatal("expected error, got nil")
+	}
+}