Article export + Bootstrap toggle + export change log

- patchScore() now accepts articles[] and returns { text, log } instead
  of a plain string. Dirty articles are re-serialized into the articles:
  block (block style, replacing any existing flow-style entries). Clean
  articles bypass the patcher entirely.
- article.isDirty is set on direct property edits so the exporter can
  distinguish directly changed entities from propagated dirty state.
- patchScore() log collects { level:'changed', path } for each patched
  article/instrument/bar, and a { level:'info', message } entry for the
  count of bar documents passed through unchanged.
- CP pane shows the export log above the status poller after each export.
- Article scope toggle replaced with Bootstrap form-check form-switch;
  hand-rolled .se-toggle CSS removed.
- Test suite updated for { text, log } return; 11 new assertions (188 total).

static/style.css

@@ -356,47 +356,19 @@
     font-family: monospace;
 }
 
-/* Two-state toggle (scope: defaults / overwrites). The label preceding the
-   switch tells the user what the two ends mean; the thumb position shows
-   which is active. Click anywhere on the track to flip. */
-.se-toggle {
-    position: relative;
-    width: 2.2rem;
-    height: 1.1rem;
-    flex-shrink: 0;
-    border: 1px solid #555;
-    border-radius: 0.55rem;
-    background: #2a2a2a;
-    cursor: pointer;
-    padding: 0;
+/* Export log (shown in CP pane after export) */
+.se-export-log {
+    font-size: 0.75rem;
+    font-family: monospace;
+    border: 1px solid #333;
+    padding: 0.3rem 0.4rem;
+    margin: 0.4rem 0;
 }
-.se-toggle::after {
-    content: '';
-    position: absolute;
-    top: 1px;
-    left: 1px;
-    width: 0.85rem;
-    height: 0.85rem;
-    border-radius: 50%;
-    background: #999;
-    transition: transform 0.12s ease, background 0.12s ease;
+.se-export-changed {
+    color: #aad4aa;
 }
-.se-toggle[aria-checked="true"] {
-    background: #2d4a2d;
-    border-color: #4a7a4a;
-}
-.se-toggle[aria-checked="true"]::after {
-    transform: translateX(1.1rem);
-    background: #b0e0b0;
-}
-.se-toggle-label {
-    font-size: 0.7rem;
+.se-export-info {
     color: #888;
-    user-select: none;
-    min-width: 4em;
-}
-.se-toggle-label.active {
-    color: #d8d8d8;
 }
 
 .se-prop-key, .se-prop-val {