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/store.js

@@ -8,6 +8,7 @@ export const store = reactive({
     synthesisStatus: null,
     isDirty: false,
     errorMessage: '',
+    exportLog: [],
 
     setFocus(path) {
         this.focusPath = path;