Add per-item exclude to the rename confirmation modal

Each row in the "Confirm Rename" plan now has a small x button that drops just that
file from the batch without closing the modal or needing to cancel and re-select
beforehand (previously it was all-or-nothing - "Exclude Selected" on the file list was
the only way to leave a file out, and only before opening Rename at all). Excluding
every row disables the confirm button and shows an empty-plan hint instead of sending
an empty batch. No Rust changes needed - this is pure plan-state filtering in the
frontend, RenamePlanEntry's shape is unchanged.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/components/RenamePanel.css

@@ -403,6 +403,31 @@
   font-weight: 600;
 }
 
+.modal-plan-remove {
+  all: unset;
+  box-sizing: border-box;
+  flex: 0 0 auto;
+  width: 22px;
+  height: 22px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  border-radius: 6px;
+  color: var(--muted-text);
+  cursor: pointer;
+}
+
+.modal-plan-remove:hover {
+  background: rgba(255, 255, 255, 0.06);
+  color: #ff8a8a;
+}
+
+.modal-plan-remove:disabled {
+  opacity: 0.35;
+  cursor: default;
+  pointer-events: none;
+}
+
 .modal-note {
   margin: 10px 0 0;
   font-size: 11px;