Apply item 0xb6340749 for issue #9

Squash of the patch of item 0xb63407496b05c7ed5580852a8b11084877e719e1f4a9a6c4ae367c9b15f22b59, final in the elffuss ledger.
Solver 0xdd8075ba73c2173b9f05957b5f1a7561600e5494; 2 approvals of round 0.

T2T-Item: 0xb63407496b05c7ed5580852a8b11084877e719e1f4a9a6c4ae367c9b15f22b59
T2T-Issue: 0x76d6986733689a0daf7f538f2068e36d2e4d9363bd01d5e0e69704ee39f48fd3
T2T-Event: 0x80803f1aa05fcaa0131d6bf26b5ee90528884780d17a0475a07c12922da3f8ca

tests/acceptance/9/CRITERIA.json

@@ -0,0 +1,12 @@
+{
+  "schema": "elffuss-t2t/criteria@2",
+  "issue": 9,
+  "criteria": [
+    {
+      "index": 1,
+      "tests": [
+        "tests/acceptance/9/criteria.test.js::criterion 1"
+      ]
+    }
+  ]
+}

tests/acceptance/9/criteria.test.js

@@ -0,0 +1,15 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+const mod = await import('../../../web/js/conversations.js')
+
+const convOf = content => ({ title: null, agent: { history: [{ role: 'user', content }] } })
+
+test('criterion 1', () => {
+  const emoji = '\u{1F600}'
+  const a39 = 'a'.repeat(39)
+  const title = mod.titleFor(convOf(a39 + emoji + 'bcd'))
+  assert.equal(title, a39 + emoji + '…')
+  assert.equal(title.isWellFormed(), true)
+
+  assert.equal(mod.titleFor(convOf('a'.repeat(60))), 'a'.repeat(40) + '…')
+})

web/js/conversations.js

@@ -41,7 +41,8 @@ export function titleFor(conv) {
   // no debe filtrarse al título de la pestaña — se muestra el texto limpio.
   const raw = firstUser.content.startsWith(GOAL_PREFIX) ? firstUser.content.slice(GOAL_PREFIX.length) : firstUser.content;
   const t = cleanTitle(raw);
-  return t.length > 40 ? t.slice(0, 40) + '…' : t || 'Nueva conversación';
+  const chars = Array.from(t);
+  return chars.length > 40 ? chars.slice(0, 40).join('') + '…' : t || 'Nueva conversación';
 }
 
 export function setProvider(mod) {