fix: a caption is boxed to its frame, and the frame stays clickable

Two faults on one picture. A block after a float keeps its box over
the float — only its lines move — so the caption on top swallowed
every click meant for the picture; the frame is lifted above the
in-flow boxes. And a caption can only sit under a side-wrapped frame
if it is boxed to it, so its span in the column is measured and
becomes the caption's indent, which also drops it clear of the float.
Measured at 100% and 150%: caption under the picture, its width, in
all four wrap modes.

src/styles/editor.css

@@ -347,6 +347,13 @@
 .paper .tiptap .image-node.image-selected {
   z-index: 25;
 }
+/* A block after a float keeps its own box over the float — only its lines move out of
+   the way — so the block on top swallows every click meant for the frame. Nothing is
+   hidden by lifting it: text flows beside a frame, never across it. A page-anchored
+   one is excluded, since it carries its own place in the stack (image.ts). */
+.paper .tiptap .image-node[data-wrap]:not([data-anchor-page]) {
+  z-index: 1;
+}
 .paper .tiptap .image-rotor {
   position: absolute;
   left: 50%;