Preserve preview harness, editor, email and task improvements

Snapshot current maintainer-preview application changes and regression fixtures for integration into lab. Excludes local runtime data, evaluation outputs and source backups. Focused Python regression selection: 140 passed; full suite not certified.

tests/emailReplyStream.test.mjs

@@ -0,0 +1,24 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import {readEmailReplyResponse} from '../static/js/emailReplyStream.js';
+
+const response = frames => new Response(frames.map(f => `data: ${JSON.stringify(f)}\n\n`).join(''),
+  {headers: {'content-type': 'text/event-stream'}});
+
+test('streams body then requires successful terminal result', async () => {
+  const seen = [];
+  const result = await readEmailReplyResponse(response([
+    {type:'reply', text:'Hi'}, {type:'reply', text:'Hi Jonathan'},
+    {type:'result', success:true, reply:'Hi Jonathan'},
+  ]), text => seen.push(text));
+  assert.deepEqual(seen, ['Hi', 'Hi Jonathan']);
+  assert.equal(result.success, true);
+});
+
+test('editing the draft stops streaming insertion', async () => {
+  await assert.rejects(readEmailReplyResponse(response([{type:'reply', text:'Hi'}]), () => false), /edited or closed/);
+});
+
+test('disconnect is not a completed draft', async () => {
+  await assert.rejects(readEmailReplyResponse(response([{type:'reply', text:'Hi'}]), () => {}), /before completion/);
+});