feat(desktop): icon mark sized to match neighbors, add drop shadow, unify screen headers

Icon:
- Mark now fills ~85% of the squircle (was 80%) so the goose reads at
  the same visual weight as first-party dock icons. Apple's template
  specifies 7.5-10% padding inside the squircle; 7.5% lands closer to
  the average first-party icon.
- Baked a drop shadow into the icon PNG: 8px offset, 18px Gaussian
  blur at ~28% black, rendered under the white squircle on its own
  layer so the blur doesn't leak into the mark. First-party macOS
  icons include this shadow in the PNG — the dock doesn't add one at
  render time. Separable Gaussian (2x 1D passes) keeps startup fast.

Screen header consistency (match Messages pattern):
- Bookmarks, Drafts, Search, Reads, Highlights: titles switched from
  headlineMedium to titleMedium.
- All five header rows now pad horizontal = 12.dp, vertical = 8.dp
  (matching ConversationListPane's "Messages" header).
- Removed the 16.dp outer wrapper padding from Bookmarks and the 16.dp
  bottom padding from Reads header — screens now sit edge-to-edge.
- DeckColumnContainer's 12.dp outer padding around column content
  removed for the same reason SinglePaneLayout's was: creates a
  `#F5F5F7` frame around every screen that reads as inconsistent
  with Messages (and every native desktop app).

https://claude.ai/code/session_01NufduPfZvYQVYwLkbCjCUo

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/platform/PlatformAppIcon.kt

@@ -25,6 +25,8 @@ import java.awt.Color
 import java.awt.RenderingHints
 import java.awt.geom.RoundRectangle2D
 import java.awt.image.BufferedImage
+import java.awt.image.ConvolveOp
+import java.awt.image.Kernel
 
 /**
  * Adapts a transparent source logo to the host OS's app-icon conventions.
@@ -74,10 +76,45 @@ object PlatformAppIcon {
         val squircleMargin = (canvas - squircleSize) / 2
         // Apple's reference corner radius on the 824-box is ~185px (≈22.45%).
         val cornerDiameter = (squircleSize * 0.4490f)
-        // Mark padding inside the squircle: 10% of the squircle size.
-        val markPadding = (squircleSize * 0.10f).toInt()
+        // Mark padding inside the squircle: 7.5% each side (~85% fill) so the
+        // mark reads at roughly the same visual weight as first-party dock icons.
+        val markPadding = (squircleSize * 0.075f).toInt()
         val markOrigin = squircleMargin + markPadding
         val markSize = squircleSize - 2 * markPadding
+        // Drop shadow under the squircle — Apple's dock icons include a subtle
+        // shadow baked into the PNG; the dock doesn't add one at render time.
+        val shadowOffset = 8
+        val shadowBlur = 18
+
+        val squircle =
+            RoundRectangle2D.Float(
+                squircleMargin.toFloat(),
+                squircleMargin.toFloat(),
+                squircleSize.toFloat(),
+                squircleSize.toFloat(),
+                cornerDiameter,
+                cornerDiameter,
+            )
+
+        // Rasterize the shadow onto its own layer so the blur doesn't leak
+        // into the white squircle or the mark.
+        val shadowLayer = BufferedImage(canvas, canvas, BufferedImage.TYPE_INT_ARGB)
+        shadowLayer.createGraphics().apply {
+            setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)
+            color = Color(0, 0, 0, 72) // ~28% black
+            val shadowShape =
+                RoundRectangle2D.Float(
+                    squircleMargin.toFloat(),
+                    (squircleMargin + shadowOffset).toFloat(),
+                    squircleSize.toFloat(),
+                    squircleSize.toFloat(),
+                    cornerDiameter,
+                    cornerDiameter,
+                )
+            fill(shadowShape)
+            dispose()
+        }
+        val blurredShadow = gaussianBlur(shadowLayer, shadowBlur)
 
         val out = BufferedImage(canvas, canvas, BufferedImage.TYPE_INT_ARGB)
         val g = out.createGraphics()
@@ -86,21 +123,13 @@ object PlatformAppIcon {
             g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC)
             g.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY)
 
-            val squircle =
-                RoundRectangle2D.Float(
-                    squircleMargin.toFloat(),
-                    squircleMargin.toFloat(),
-                    squircleSize.toFloat(),
-                    squircleSize.toFloat(),
-                    cornerDiameter,
-                    cornerDiameter,
-                )
-            g.composite = AlphaComposite.Src
+            // Shadow first, then the white squircle on top, then the mark.
+            g.composite = AlphaComposite.SrcOver
+            g.drawImage(blurredShadow, 0, 0, null)
+
             g.color = Color(0xFFFFFF)
             g.fill(squircle)
 
-            // Composite the source logo on top, scaled into the padded area.
-            g.composite = AlphaComposite.SrcOver
             g.clip = squircle
             g.drawImage(source, markOrigin, markOrigin, markSize, markSize, null)
         } finally {
@@ -108,4 +137,30 @@ object PlatformAppIcon {
         }
         return out
     }
+
+    /**
+     * Separable Gaussian blur via [ConvolveOp]. Splits the 2D kernel into two
+     * 1D passes (horizontal then vertical) — O(N) per pixel instead of O(N²)
+     * for a radius-N blur, which keeps startup snappy even at 1024x1024.
+     */
+    private fun gaussianBlur(
+        src: BufferedImage,
+        radius: Int,
+    ): BufferedImage {
+        if (radius < 1) return src
+        val size = radius * 2 + 1
+        val sigma = radius / 2f
+        val kernel = FloatArray(size)
+        var sum = 0f
+        for (i in 0 until size) {
+            val x = (i - radius).toFloat()
+            kernel[i] = kotlin.math.exp(-(x * x) / (2f * sigma * sigma))
+            sum += kernel[i]
+        }
+        for (i in 0 until size) kernel[i] /= sum
+
+        val horiz = ConvolveOp(Kernel(size, 1, kernel), ConvolveOp.EDGE_NO_OP, null)
+        val vert = ConvolveOp(Kernel(1, size, kernel), ConvolveOp.EDGE_NO_OP, null)
+        return vert.filter(horiz.filter(src, null), null)
+    }
 }

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/BookmarksScreen.kt

@@ -252,12 +252,12 @@ fun BookmarksScreen(
             modifier =
                 Modifier
                     .fillMaxWidth()
-                    .padding(16.dp),
+                    .padding(horizontal = 12.dp, vertical = 8.dp),
             verticalAlignment = Alignment.CenterVertically,
         ) {
             Text(
                 text = "Bookmarks",
-                style = MaterialTheme.typography.headlineMedium,
+                style = MaterialTheme.typography.titleMedium,
                 color = MaterialTheme.colorScheme.onBackground,
             )
 

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/DraftsScreen.kt

@@ -68,13 +68,16 @@ fun DraftsScreen(
 
     Column(modifier = Modifier.fillMaxSize()) {
         Row(
-            modifier = Modifier.fillMaxWidth(),
+            modifier =
+                Modifier
+                    .fillMaxWidth()
+                    .padding(horizontal = 12.dp, vertical = 8.dp),
             horizontalArrangement = Arrangement.SpaceBetween,
             verticalAlignment = Alignment.CenterVertically,
         ) {
             Text(
                 "Drafts",
-                style = MaterialTheme.typography.headlineMedium,
+                style = MaterialTheme.typography.titleMedium,
                 color = MaterialTheme.colorScheme.onBackground,
             )
             Button(onClick = { onOpenEditor(null) }) {

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/ReadsScreen.kt

@@ -294,7 +294,10 @@ fun ReadsScreen(
     Column(modifier = Modifier.fillMaxSize()) {
         // Header — wraps on narrow columns
         FlowRow(
-            modifier = Modifier.fillMaxWidth().padding(bottom = 16.dp),
+            modifier =
+                Modifier
+                    .fillMaxWidth()
+                    .padding(horizontal = 12.dp, vertical = 8.dp),
             horizontalArrangement = Arrangement.SpaceBetween,
             verticalArrangement = Arrangement.spacedBy(8.dp),
         ) {
@@ -305,7 +308,7 @@ fun ReadsScreen(
                 ) {
                     Text(
                         "Reads",
-                        style = MaterialTheme.typography.headlineMedium,
+                        style = MaterialTheme.typography.titleMedium,
                         color = MaterialTheme.colorScheme.onBackground,
                     )
 

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/SearchScreen.kt

@@ -331,13 +331,16 @@ fun SearchScreen(
 
         // Title row
         Row(
-            modifier = Modifier.fillMaxWidth(),
+            modifier =
+                Modifier
+                    .fillMaxWidth()
+                    .padding(horizontal = 12.dp, vertical = 8.dp),
             horizontalArrangement = Arrangement.SpaceBetween,
             verticalAlignment = Alignment.CenterVertically,
         ) {
             Text(
                 "Search",
-                style = MaterialTheme.typography.headlineMedium,
+                style = MaterialTheme.typography.titleMedium,
                 color = MaterialTheme.colorScheme.onBackground,
             )
             Text(

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/deck/DeckColumnContainer.kt

@@ -24,7 +24,6 @@ import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
 import androidx.compose.material3.HorizontalDivider
 import androidx.compose.material3.MaterialTheme
@@ -130,9 +129,10 @@ fun DeckColumnContainer(
 
         HorizontalDivider()
 
-        Box(
-            modifier = Modifier.fillMaxSize().padding(12.dp),
-        ) {
+        // Content runs edge-to-edge; each screen adds its own header padding
+        // to match the Messages pattern (padding(horizontal = 12, vertical = 8)
+        // on the title row, no outer wrapper).
+        Box(modifier = Modifier.fillMaxSize()) {
             // Always keep RootContent composed so state (e.g. search results) survives navigation
             RootContent(
                 columnType = column.type,

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/ui/highlights/MyHighlightsScreen.kt

@@ -74,11 +74,12 @@ fun MyHighlightsScreen(
     Column(modifier = Modifier.fillMaxSize()) {
         Text(
             "Highlights",
-            style = MaterialTheme.typography.headlineMedium,
+            style = MaterialTheme.typography.titleMedium,
             color = MaterialTheme.colorScheme.onBackground,
+            modifier = Modifier.padding(horizontal = 12.dp, vertical = 8.dp),
         )
 
-        Spacer(Modifier.height(16.dp))
+        Spacer(Modifier.height(8.dp))
 
         if (allHighlights.isEmpty()) {
             EmptyState(