test(v0.4): cover SummarizeFromDiff and FormatLaunchContext

internal/session/summary_test.go

@@ -107,3 +107,65 @@ func TestReadSummaryCorruptReturnsError(t *testing.T) {
 		t.Error("expected error reading corrupt summary")
 	}
 }
+
+func TestSummarizeFromDiff(t *testing.T) {
+	start := time.Date(2026, 4, 21, 14, 30, 22, 0, time.UTC)
+	end := start.Add(90 * time.Second)
+
+	diff := &ManifestDiff{
+		Added:    []string{"output/result.md"},
+		Modified: []string{"notes.md"},
+		Deleted:  []string{},
+	}
+	endManifest := &Manifest{
+		CapturedAt: end,
+		Files: []FileEntry{
+			{Path: "notes.md", Size: 200, Mtime: end},
+			{Path: "output/result.md", Size: 100, Mtime: end},
+		},
+	}
+
+	s := SummarizeFromDiff("sid", "host", "claude", "local", start, end, diff, endManifest)
+
+	if s.DurationSeconds != 90 {
+		t.Errorf("DurationSeconds: got %d, want 90", s.DurationSeconds)
+	}
+	if !s.NotesUpdated {
+		t.Error("NotesUpdated should be true")
+	}
+	if len(s.EndManifest) != 2 {
+		t.Errorf("EndManifest length: got %d, want 2", len(s.EndManifest))
+	}
+}
+
+func TestFormatLaunchContextNilReturnsEmpty(t *testing.T) {
+	if got := FormatLaunchContext(nil); got != "" {
+		t.Errorf("expected empty string for nil summary, got %q", got)
+	}
+}
+
+func TestFormatLaunchContextRendersChanged(t *testing.T) {
+	start := time.Date(2026, 4, 21, 14, 30, 22, 0, time.UTC)
+	end := start.Add(1 * time.Hour)
+	s := &SessionSummary{
+		StartedAt:     start,
+		EndedAt:       end,
+		Hostname:      "warren-desktop",
+		Agent:         "claude",
+		FilesModified: []string{"notes.md"},
+		FilesAdded:    []string{"output/plan.md", "output/schema.sql", "output/notes.md"},
+	}
+	got := FormatLaunchContext(s)
+	for _, want := range []string{
+		"[ctask] Last session:",
+		"warren-desktop",
+		"claude",
+		"Changed:",
+		"notes.md",
+		"(+2 more)",
+	} {
+		if !strings.Contains(got, want) {
+			t.Errorf("FormatLaunchContext missing %q in:\n%s", want, got)
+		}
+	}
+}