feat(audit): full-history JSONL export in the actions menu

The menu so far only exported the current view (type + search
filter over the page 100-event window). A second action now fetches
the complete event history of the active project scope in one
EventLog call (the RPC has no cursor and no server-side cap) and
writes it as JSONL. Serialisation extracted to a top-level function
with unit tests; a stale comment advertising the never-shipped
"chain audit export" command now names "chain admin events --json".
Studio 0.73.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

test/audit_filter_test.dart

@@ -1,5 +1,8 @@
-// Free-text audit search — the match function behind the audit
-// page's search field and JSONL export ("current view" semantics).
+// Free-text audit search and JSONL serialisation — the functions
+// behind the audit page's search field and both export actions
+// ("current view" and full history).
+
+import 'dart:convert';
 
 import 'package:flutter_test/flutter_test.dart';
 
@@ -46,4 +49,47 @@ void main() {
     expect(matchesAuditQuery(_event(), 'nichtvorhanden'), isFalse);
     expect(matchesAuditQuery(_event(flow: null, error: null), 'flow'), isFalse);
   });
+
+  test('JSONL export: one line per event, order kept, trailing newline', () {
+    final out = auditEventsToJsonl([
+      _event(flow: 'first'),
+      _event(flow: 'second'),
+    ]);
+    expect(out.endsWith('\n'), isTrue);
+    final lines = out.trimRight().split('\n');
+    expect(lines, hasLength(2));
+    expect(jsonDecode(lines[0])['flow'], 'first');
+    expect(jsonDecode(lines[1])['flow'], 'second');
+  });
+
+  test('JSONL export: absent optional fields are omitted, not null', () {
+    final line =
+        jsonDecode(auditEventsToJsonl([_event()]).trimRight()) as Map;
+    expect(line['event_id'], 'evt-1');
+    expect(line['type'], 'step.completed');
+    expect(line['timestamp'], '2026-07-18T00:00:00.000Z');
+    expect(line.containsKey('flow'), isFalse);
+    expect(line.containsKey('error'), isFalse);
+    expect(line.containsKey('project'), isFalse);
+    expect(line.containsKey('duration_ms'), isFalse);
+  });
+
+  test('JSONL export: set fields appear under their wire names', () {
+    final line = jsonDecode(auditEventsToJsonl([
+      _event(
+        flow: 'rechnungslauf',
+        step: 'extract',
+        module: 'debug.echo',
+        error: 'timeout',
+        detail: '{"n":1}',
+        project: 'stromnetz',
+      ),
+    ]).trimRight()) as Map;
+    expect(line['flow'], 'rechnungslauf');
+    expect(line['step'], 'extract');
+    expect(line['module'], 'debug.echo');
+    expect(line['error'], 'timeout');
+    expect(line['detail'], '{"n":1}');
+    expect(line['project'], 'stromnetz');
+  });
 }