fix: images resize with window, blend toolbar into content

Images sized themselves once at restyle time and never got
re-measured on a pure window/pane resize (no text change, no image
fingerprint change) - so they'd stay whatever width they were last
styled at. The engine already had the fix for exactly this shape of
problem for wide tables (a stamped .scrollableBlockFullRange
attribute triggers a targeted restyle on width change), and the
shared image-rendering helper already had a restyleOnWidthChange flag
to opt into it - just never passed at the image call sites. Wired it
on for both ![]() and ![[embed]] rendering.

Also makes the titlebar/toolbar strip blend into the sidebar's
background instead of reading as a separate bar, matching Mail/Notes/
Finder - titlebarAppearsTransparent + fullSizeContentView via a small
NSViewRepresentable, same "reach into NSWindow directly" pattern
applyMacAppearance() already uses since SwiftUI's WindowGroup has no
direct API for either.

Outpost/OutpostApp.swift

@@ -34,6 +34,7 @@ struct OutpostApp: App {
                 .onAppear { applyMacAppearance() }
                 .onChange(of: appearance) { _, _ in applyMacAppearance() }
                 .logoutConfirmationDialog(isPresented: $isShowingLogoutConfirmation, session: session)
+                .background(TransparentTitlebarWindowAccessor())
                 #endif
         }
         #if os(macOS)
@@ -101,3 +102,27 @@ struct OutpostApp: App {
     }
     #endif
 }
+
+#if os(macOS)
+/// Makes the titlebar/toolbar strip blend into the sidebar's own background
+/// instead of reading as a separate bar — same look as Mail/Notes/Finder.
+/// SwiftUI's `WindowGroup` exposes no direct hook for this, so this reaches
+/// into the underlying `NSWindow` the way `applyMacAppearance()` above
+/// reaches into `NSApp` for the same reason (no SwiftUI-level API exists).
+/// A `View` (not the window itself) is what actually needs to extend under
+/// the now-transparent titlebar — `.fullSizeContentView` just makes room;
+/// the sidebar's `.background` already does the rest with no other change.
+private struct TransparentTitlebarWindowAccessor: NSViewRepresentable {
+    func makeNSView(context: Context) -> NSView {
+        let view = NSView()
+        DispatchQueue.main.async {
+            guard let window = view.window else { return }
+            window.titlebarAppearsTransparent = true
+            window.styleMask.insert(.fullSizeContentView)
+        }
+        return view
+    }
+
+    func updateNSView(_ nsView: NSView, context: Context) {}
+}
+#endif

Vendor/swift-markdown-engine/Sources/MarkdownEngine/Styling/MarkdownStyler+Images.swift

@@ -75,6 +75,7 @@ extension MarkdownStyler {
                     paragraphSpacing: imageEmbedConfig.paragraphSpacing,
                     alignment: .left,
                     mode: .visibleSource(imageGap: imageEmbedConfig.imageGap),
+                    restyleOnWidthChange: true,
                     ctx: ctx,
                     attrs: &attrs
                 )
@@ -88,6 +89,7 @@ extension MarkdownStyler {
                     paragraphSpacing: imageEmbedConfig.paragraphSpacing,
                     alignment: .left,
                     mode: .collapsedSource(markerTexts: ["![", "]", "(", ")"]),
+                    restyleOnWidthChange: true,
                     ctx: ctx,
                     attrs: &attrs
                 )
@@ -166,6 +168,7 @@ extension MarkdownStyler {
                         paragraphSpacing: imageEmbedConfig.paragraphSpacing,
                         alignment: .left,
                         mode: .visibleSource(imageGap: imageEmbedConfig.imageGap),
+                        restyleOnWidthChange: true,
                         ctx: ctx,
                         attrs: &attrs
                     )
@@ -179,6 +182,7 @@ extension MarkdownStyler {
                         paragraphSpacing: imageEmbedConfig.paragraphSpacing,
                         alignment: .left,
                         mode: .collapsedSource(markerTexts: ["![[", "]]"]),
+                        restyleOnWidthChange: true,
                         ctx: ctx,
                         attrs: &attrs
                     )

Vendor/swift-markdown-engine/Sources/MarkdownEngine/TextView/NativeTextView/NativeTextView+FrameAndOverscroll.swift

@@ -269,21 +269,25 @@ extension NativeTextView {
 
         recalcOverscroll(for: scrollView, targetWidth: newSize.width, debugTag: "setFrameSize")
 
-        // Width change → only rendered table paragraphs need restyling. Their image
-        // width can change, and an initially narrow table can become scrollable.
+        // Width change → only paragraphs tagged `.scrollableBlockFullRange`
+        // (rendered tables and standalone images — see appendRenderedStandaloneBlock's
+        // `restyleOnWidthChange`) need restyling. Their display size is measured
+        // off the container width, and an initially narrow table can become
+        // scrollable.
         if widthChanged {
             DispatchQueue.main.async { [weak self] in
                 guard let self = self else { return }
                 if self.configuration.readingWidth == nil {
-                    self.restyleTableParagraphsForWidthChange()
+                    self.restyleWidthDependentParagraphsForWidthChange()
                 }
                 self.updateWideTableOverlays()
             }
         }
     }
 
-    /// Restyle only table paragraphs via stamped anchor ranges; avoids re-tokenizing the doc.
-    private func restyleTableParagraphsForWidthChange() {
+    /// Restyle only width-dependent paragraphs (tables, standalone images) via
+    /// stamped anchor ranges; avoids re-tokenizing the doc.
+    private func restyleWidthDependentParagraphsForWidthChange() {
         guard let storage = textStorage,
               let coord = delegate as? NativeTextViewCoordinator else { return }
         var ranges: [NSRange] = []