Implement stable serialization and restoration for dock layouts, including auto-hidden and floating panels

- Add `persistence.rs` for stable serialization of dock layouts without runtime identifiers.
- Introduce `preview.rs` for geometry handling of dock drop previews.
- Create `sizing.rs` to manage content-aware sizing policies and constraint solving for dock panels.
- Implement `welcome.rs` to provide a welcome surface when no documents are open, featuring New and Open actions.

tools/panel-tuner/src/main.rs

@@ -17,24 +17,36 @@ fn main() {
         eprintln!("Usage: panel-tuner <config.json>");
         std::process::exit(1);
     }
-    let config: Config = serde_json::from_reader(
-        std::fs::File::open(&args[1]).expect("Failed to open config"),
-    ).expect("Failed to parse config");
+    let config: Config =
+        serde_json::from_reader(std::fs::File::open(&args[1]).expect("Failed to open config"))
+            .expect("Failed to parse config");
 
     std::fs::create_dir_all(&config.output_dir).ok();
 
     let mut best: Option<(Vec<f32>, f64, PathBuf)> = None;
-    let combinations = cartesian_product(&config.parameters.iter().map(|p| p.1.clone()).collect::<Vec<_>>());
+    let combinations = cartesian_product(
+        &config
+            .parameters
+            .iter()
+            .map(|p| p.1.clone())
+            .collect::<Vec<_>>(),
+    );
 
     for (idx, values) in combinations.iter().enumerate() {
         let out = config.output_dir.join(format!("capture_{}.png", idx));
         let mut cmd = Command::new(&config.gui_binary);
-        for (name, value) in config.parameters.iter().map(|p| p.0.clone()).zip(values.iter()) {
-            cmd.env(format!("HCIE_TUNER_{}", name.to_uppercase()), value.to_string());
+        for (name, value) in config
+            .parameters
+            .iter()
+            .map(|p| p.0.clone())
+            .zip(values.iter())
+        {
+            cmd.env(
+                format!("HCIE_TUNER_{}", name.to_uppercase()),
+                value.to_string(),
+            );
         }
-        cmd.arg("--screenshot-panel")
-            .arg(&config.panel)
-            .arg(&out);
+        cmd.arg("--screenshot-panel").arg(&config.panel).arg(&out);
 
         let status = cmd.status().expect("Failed to run GUI binary");
         if !status.success() {
@@ -44,10 +56,7 @@ fn main() {
 
         let diff_out = config.output_dir.join(format!("diff_{}.png", idx));
         let mae = run_diff(&config.target, &out, &diff_out);
-        eprintln!(
-            "Run {}: params={:?} MAE={:.6}",
-            idx, values, mae
-        );
+        eprintln!("Run {}: params={:?} MAE={:.6}", idx, values, mae);
         if best.as_ref().map_or(true, |b| mae < b.1) {
             best = Some((values.clone(), mae, out.clone()));
         }

tools/screenshot-diff/src/main.rs

@@ -8,12 +8,23 @@ fn main() {
     }
     let target_path = PathBuf::from(&args[1]);
     let actual_path = PathBuf::from(&args[2]);
-    let save_diff = args.iter().position(|a| a == "--save-diff").and_then(|i| args.get(i + 1)).map(PathBuf::from);
+    let save_diff = args
+        .iter()
+        .position(|a| a == "--save-diff")
+        .and_then(|i| args.get(i + 1))
+        .map(PathBuf::from);
 
-    let target = image::open(&target_path).expect("Failed to open target").to_rgba8();
-    let actual = image::open(&actual_path).expect("Failed to open actual").to_rgba8();
+    let target = image::open(&target_path)
+        .expect("Failed to open target")
+        .to_rgba8();
+    let actual = image::open(&actual_path)
+        .expect("Failed to open actual")
+        .to_rgba8();
 
-    let (w, h) = (target.width().min(actual.width()), target.height().min(actual.height()));
+    let (w, h) = (
+        target.width().min(actual.width()),
+        target.height().min(actual.height()),
+    );
     if w == 0 || h == 0 {
         eprintln!("One of the images has zero size");
         std::process::exit(1);