feat: add user-selectable aspect ratio and resolution per thread

Adds a two-step new thread modal: step one picks mode, step two
configures aspect ratio (Art mode only, six options) and resolution
(all modes: 1K/2K/4K). Settings are stored on the thread and forwarded
to the Gemini API on every send, retry, and edit. Also regenerates
icon.ico with Python to produce a clean all-BMP ICO compatible with
both Tauri's proc macro and llvm-rc cross-compilation.

src-tauri/src/gemini.rs

@@ -46,12 +46,19 @@ fn build_safety_settings() -> Value {
     ])
 }
 
-fn build_generation_config(mode: &str) -> Value {
+fn build_generation_config(
+    mode: &str,
+    aspect_ratio: Option<&str>,
+    image_size: &str,
+) -> Value {
     let image_config = match mode {
-        "avatar" => json!({ "aspectRatio": "1:1", "imageSize": "4K" }),
-        "art"    => json!({ "aspectRatio": "16:9", "imageSize": "4K" }),
+        "avatar" => json!({ "aspectRatio": "1:1", "imageSize": image_size }),
+        "art" => {
+            let ratio = aspect_ratio.unwrap_or("16:9");
+            json!({ "aspectRatio": ratio, "imageSize": image_size })
+        }
         // replace mode: omit aspectRatio so the model infers it from the source image
-        _        => json!({ "imageSize": "4K" }),
+        _ => json!({ "imageSize": image_size }),
     };
     json!({
         "imageConfig": image_config,
@@ -111,6 +118,8 @@ fn build_user_gemini_parts(
 pub async fn call_gemini(
     api_key: String,
     mode: String,
+    aspect_ratio: Option<String>,
+    image_size: String,
     history: Vec<ThreadMessage>,
     user_text: Option<String>,
     user_image_base64: Option<String>,
@@ -160,7 +169,11 @@ pub async fn call_gemini(
 
     contents.push(json!({"role": "user", "parts": user_parts}));
 
-    let generation_config = build_generation_config(mode.as_str());
+    let generation_config = build_generation_config(
+        mode.as_str(),
+        aspect_ratio.as_deref(),
+        image_size.as_str(),
+    );
     let safety_settings = build_safety_settings();
 
     let request_body = json!({
@@ -252,8 +265,13 @@ pub async fn call_gemini(
     let candidates_tokens = usage["candidatesTokenCount"].as_u64().unwrap_or(0);
     let image_part_count = result_parts.iter().filter(|p| p.part_type == "image").count() as u64;
 
-    // Image output tokens (4K = 2000 tokens each) billed at $120/1M tokens
-    let image_output_tokens = image_part_count * 2_000_u64;
+    // Image output tokens per image vary by resolution, billed at $120/1M tokens
+    let tokens_per_image: u64 = match image_size.as_str() {
+        "1K" => 500,
+        "2K" => 1_000,
+        _    => 2_000, // 4K default
+    };
+    let image_output_tokens = image_part_count * tokens_per_image;
     // Remaining candidates tokens are text/thinking, billed at $12/1M tokens
     let text_output_tokens = candidates_tokens.saturating_sub(image_output_tokens);
 

src-tauri/src/lib.rs

@@ -49,13 +49,24 @@ async fn save_config(config: Config) -> Result<(), String> {
 async fn send_message(
     api_key: String,
     mode: String,
+    aspect_ratio: Option<String>,
+    image_size: String,
     history: Vec<ThreadMessage>,
     user_text: Option<String>,
     user_image_base64: Option<String>,
     user_image_mime: Option<String>,
 ) -> Result<SendMessageResult, String> {
-    let (parts, cost_usd) =
-        call_gemini(api_key, mode, history, user_text, user_image_base64, user_image_mime).await?;
+    let (parts, cost_usd) = call_gemini(
+        api_key,
+        mode,
+        aspect_ratio,
+        image_size,
+        history,
+        user_text,
+        user_image_base64,
+        user_image_mime,
+    )
+    .await?;
     Ok(SendMessageResult { parts, cost_usd })
 }
 

src-tauri/src/storage.rs

@@ -25,11 +25,19 @@ pub struct ThreadMessage {
     pub cost_usd: Option<f64>,
 }
 
+fn default_image_size() -> String {
+    "4K".to_string()
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Thread {
     pub id: String,
     pub name: String,
     pub mode: String,
+    #[serde(rename = "aspectRatio", skip_serializing_if = "Option::is_none")]
+    pub aspect_ratio: Option<String>,
+    #[serde(rename = "imageSize", default = "default_image_size")]
+    pub image_size: String,
     pub messages: Vec<ThreadMessage>,
     #[serde(rename = "createdAt")]
     pub created_at: i64,