fix(extraction): handle unknown-table ops in stable height reservation

When all operations target unknown tables, groupOperationsByTable
returns empty groups but hasOps is true. Fall back to rendered section
line count instead of returning 0 from stablePreviewLines, preserving
overlay sizing behavior for this edge case.

Author: cpcloud

internal/app/extraction_render.go

@@ -155,13 +155,19 @@ func (m *Model) buildExtractionPipelineOverlay(
 		// Reserve height for the tallest preview tab so the overlay
 		// doesn't jump when switching tabs in explore mode.
 		previewLines = stablePreviewLines(ex.previewGroups)
-		// Pad rendered section to stable height so the overlay
-		// doesn't shrink when a shorter tab is displayed.
-		actualLines := strings.Count(previewSection, "\n")
-		targetLines := previewLines - 2 // -2: sep+blank added as separate parts
-		for actualLines < targetLines {
-			previewSection += "\n"
-			actualLines++
+		if previewLines == 0 {
+			// Fallback for unknown-table ops where no preview groups
+			// are generated: use rendered section's actual line count.
+			previewLines = strings.Count(previewSection, "\n") + 2
+		} else {
+			// Pad rendered section to stable height so the overlay
+			// doesn't shrink when a shorter tab is displayed.
+			actualLines := strings.Count(previewSection, "\n")
+			targetLines := previewLines - 2 // -2: sep+blank added as separate parts
+			for actualLines < targetLines {
+				previewSection += "\n"
+				actualLines++
+			}
 		}
 	}
 

internal/app/extraction_test.go

@@ -3689,3 +3689,26 @@ func TestExploreMode_TabPersistsOnExit(t *testing.T) {
 	assert.Contains(t, plain, "Total",
 		"pipeline mode should show last-explored tab content")
 }
+
+func TestExploreMode_UnknownTableOverlayStable(t *testing.T) {
+	t.Parallel()
+	// Unknown tables produce no preview groups but hasOps is still true.
+	// Overlay should render without panicking and maintain stable height.
+	m := newPreviewModel(t, []extract.Operation{
+		{Action: "create", Table: "unknown_table", Data: map[string]any{"x": "y"}},
+	})
+
+	out := m.buildExtractionPipelineOverlay(100, 90, "test")
+	plain := ansi.Strip(out)
+	lines := strings.Count(out, "\n")
+
+	assert.Greater(t, lines, 0, "overlay should render with nonzero height")
+	assert.Contains(t, plain, "no operations",
+		"should show fallback text for unknown tables")
+
+	// Build again -- height should be identical (stable).
+	out2 := m.buildExtractionPipelineOverlay(100, 90, "test")
+	lines2 := strings.Count(out2, "\n")
+	assert.Equal(t, lines, lines2,
+		"overlay height should be stable across renders")
+}