feat: single tall comic strip with consistent characters and more dramatic narration

- Replace 3 separate comic pages with one 9:16 tall comic_strip.png
- Prompt explicitly requests 3 vertically stacked panels with consistent characters
- Add AspectRatio field to SearchOptions; NanoBanana uses it when set
- Make cinematic narration instruction more dramatic (movie trailer narrator style)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

3 files changed, 23 insertions, 13 deletions

diff --git a/internal/image/nanobanana.go b/internal/image/nanobanana.go
index 4e99dfa..8bcd945 100644
--- a/internal/image/nanobanana.go
+++ b/internal/image/nanobanana.go
@@ -56,8 +56,8 @@ var newNanoBananaClient = genai.NewClient
 var nanoBananaGenerateText = func(ctx context.Context, c *NanoBananaClient, model, systemPrompt, userPrompt string, temperature float32, maxOutputTokens int32) (string, error) {
 	return c.generateText(ctx, model, systemPrompt, userPrompt, temperature, maxOutputTokens)
 }
-var nanoBananaGenerateImage = func(ctx context.Context, c *NanoBananaClient, prompt string) ([]byte, string, error) {
-	return c.generateImage(ctx, prompt)
+var nanoBananaGenerateImage = func(ctx context.Context, c *NanoBananaClient, prompt, aspectRatio string) ([]byte, string, error) {
+	return c.generateImage(ctx, prompt, aspectRatio)
 }
 
 // NewNanoBananaClient creates a new Nano Banana client.
@@ -105,10 +105,16 @@ func (c *NanoBananaClient) Search(ctx context.Context, opts *SearchOptions) ([]S
 		c.PromptCallback(prompt)
 	}
 
+	// Resolve aspect ratio: use caller override if provided, else the default.
+	aspectRatio := nanoBananaAspectRatio
+	if opts.AspectRatio != "" {
+		aspectRatio = opts.AspectRatio
+	}
+
 	fmt.Printf("Nano Banana Image Generation Prompt (%d chars): %s\n", len(prompt), prompt)
-	fmt.Printf("Nano Banana Image Generation: Using model '%s' with aspect ratio '%s'\n", c.modelName(), nanoBananaAspectRatio)
+	fmt.Printf("Nano Banana Image Generation: Using model '%s' with aspect ratio '%s'\n", c.modelName(), aspectRatio)
 
-	imageBytes, mimeType, err := nanoBananaGenerateImage(ctx, c, prompt)
+	imageBytes, mimeType, err := nanoBananaGenerateImage(ctx, c, prompt, aspectRatio)
 	if err != nil {
 		if searchErr, ok := err.(*SearchError); ok {
 			return nil, searchErr
@@ -380,11 +386,14 @@ func (c *NanoBananaClient) generateText(ctx context.Context, model, systemPrompt
 	return text, nil
 }
 
-func (c *NanoBananaClient) generateImage(ctx context.Context, prompt string) ([]byte, string, error) {
+func (c *NanoBananaClient) generateImage(ctx context.Context, prompt, aspectRatio string) ([]byte, string, error) {
+	if aspectRatio == "" {
+		aspectRatio = nanoBananaAspectRatio
+	}
 	cfg := &genai.GenerateContentConfig{
 		ResponseModalities: []string{string(genai.ModalityImage)},
 		ImageConfig: &genai.ImageConfig{
-			AspectRatio: nanoBananaAspectRatio,
+			AspectRatio: aspectRatio,
 		},
 	}
 
diff --git a/internal/image/nanobanana_test.go b/internal/image/nanobanana_test.go
index 88cc43c..c9cfb61 100644
--- a/internal/image/nanobanana_test.go
+++ b/internal/image/nanobanana_test.go
@@ -71,7 +71,7 @@ func TestNanoBananaClient_Search_CustomPromptSkipsTextGeneration(t *testing.T) {
 	}
 
 	var gotPrompt string
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt, _ string) ([]byte, string, error) {
 		gotPrompt = prompt
 		return mustPNGBytes(t), "image/png", nil
 	}
@@ -149,7 +149,7 @@ func TestNanoBananaClient_Search_GeneratedPromptFlow(t *testing.T) {
 		return "", nil
 	}
 
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt, _ string) ([]byte, string, error) {
 		gotPrompt = prompt
 		return mustJPEGBytes(t), "image/jpeg", nil
 	}
@@ -249,7 +249,7 @@ func TestNanoBananaClient_Search_TranslationFailureFallsBackToQuery(t *testing.T
 		return "", nil
 	}
 
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt, _ string) ([]byte, string, error) {
 		return mustPNGBytes(t), "image/png", nil
 	}
 
@@ -297,7 +297,7 @@ func TestNanoBananaClient_Search_TrivialSceneFallsBackToSubjectPrompt(t *testing
 	}
 
 	var gotPrompt string
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, prompt, _ string) ([]byte, string, error) {
 		gotPrompt = prompt
 		return mustPNGBytes(t), "image/png", nil
 	}
@@ -342,7 +342,7 @@ func TestNanoBananaClient_Search_ImageGenerationError(t *testing.T) {
 		return "", nil
 	}
 
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, _ string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, _, _ string) ([]byte, string, error) {
 		return nil, "", fmt.Errorf("image generation failed")
 	}
 
@@ -376,7 +376,7 @@ func TestNanoBananaClient_Search_CustomPromptPreservesTranslationMetadata(t *tes
 		t.Fatal("unexpected text generation for custom prompt")
 		return "", nil
 	}
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, _ string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, _, _ string) ([]byte, string, error) {
 		return mustPNGBytes(t), "image/png", nil
 	}
 
@@ -409,7 +409,7 @@ func TestNanoBananaClient_Search_CustomPromptIgnoresWhitespaceTranslation(t *tes
 		t.Fatal("unexpected text generation for custom prompt")
 		return "", nil
 	}
-	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, _ string) ([]byte, string, error) {
+	nanoBananaGenerateImage = func(_ context.Context, _ *NanoBananaClient, _, _ string) ([]byte, string, error) {
 		return mustPNGBytes(t), "image/png", nil
 	}
 
diff --git a/internal/image/search.go b/internal/image/search.go
index be20731..8de97e0 100644
--- a/internal/image/search.go
+++ b/internal/image/search.go
@@ -28,6 +28,7 @@ type SearchOptions struct {
 	ImageType    string // Type: "photo", "illustration", "vector", "all"
 	Orientation  string // Orientation: "horizontal", "vertical", "all"
 	CustomPrompt string // Custom prompt for AI image generation
+	AspectRatio  string // Override aspect ratio (e.g. "9:16"); empty = provider default
 }
 
 // DefaultSearchOptions returns sensible defaults for Bulgarian word searches