fix(slideover): discard-confirm on new->new switch (Ctrl+Shift+A)

Opening a fresh new entry while a dirty unsaved one was open skipped the
discard prompt: both soState.id and id are null, so soState.id !== id was
false and "switching" never triggered. Existing->anything worked (ids
differ). OR in the null/null case.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/app.js

@@ -3829,9 +3829,12 @@ async function openSlideOver(id, opts) {
     // changes would silently drop them — gate on the same confirm dialog
     // used by close paths. Only fires when the panel is already open AND
     // we're actually moving to a different target.
+    // A "switch" = the panel is open on a different target. soState.id !== id
+    // catches every cross-id case EXCEPT new→new (both ids null), which is
+    // still a real switch (a dirty unsaved new entry replaced by a fresh one,
+    // e.g. Ctrl+Shift+A) — so OR that case in explicitly.
     const switching = $('#slideover').classList.contains('is-open') &&
-                      soState && (soState.id !== id) &&
-                      !(isNew && soState.id == null && soState.id === id);
+                      soState && (soState.id !== id || (id == null && soState.id == null));
     if (switching && state.confirmOnUnsaved && isSoDirty()) {
         const ok = await confirmDialog({
             title:   'Discard unsaved changes?',