Search: a word with a leading ^ matches at a word's start only

"^zed" finds "Zed Dead", "The_Zed_Files", not "Facialized": a regex on
release_texts, (^|[^[:alnum:]]) before the word, which the trigram index
serves (homelab: 551 texts for ^zed against 6,606 for zed, 35 ms warm).
Words without ^ match anywhere as before; the search box says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/functional/releases_api.spec.ts

@@ -138,4 +138,26 @@ test.group('Releases API', (group) => {
     const list = (await client.get('/api/v1/releases?q=locked movie')).body() as { releases: { passwordKnown: boolean }[] }
     assert.isTrue(list.releases[0].passwordKnown)
   })
+
+  test('a word with a leading ^ matches at a word start only; without it anywhere', async ({ client, assert }) => {
+    const [g] = await db.table('groups').insert({ name: GROUP, priority: 1 }).returning('id')
+    const [n] = await db.table('nodes').insert({ name: 'api-node' }).returning('id')
+    const [r] = await db.table('ranges').insert({ group_id: g.id, start_id: 1, end_id: 1000, next_id: 1, status: 'leased', node_id: n.id }).returning('id')
+    const indexer = new RangeIndexer({ group: GROUP, start: 1, end: 1000, rules: { ...DEFAULT_RULES, samplePercent: 0, droppedSignatures: [], priorities: { [GROUP]: 1 } } })
+    indexer.add([
+      ...file('Zed.Dead.2019.1080p.mkv', 'Zed.Dead.2019 [1/1]', 2, 100),
+      ...file('The_Zed_Files.S01E01.mkv', 'The_Zed_Files.S01E01 [1/1]', 2, 200),
+      ...file('Babe.Facialized.2017.mkv', 'Babe.Facialized.2017 [1/1]', 2, 300),
+    ], 1001)
+    indexer.finish()
+    await BatchStore.store(Number(r.id), Number(n.id), indexer.take())
+
+    const names = async (q: string) =>
+      ((await client.get(`/api/v1/releases?q=${encodeURIComponent(q)}`)).body() as { releases: { name: string }[] }).releases.map((x) => x.name).sort()
+    assert.lengthOf(await names('zed'), 3)
+    assert.deepEqual(await names('^zed'), ['The_Zed_Files S01E01', 'Zed Dead 2019'])
+    assert.deepEqual(await names('^zed dead'), ['Zed Dead 2019'])
+    // Regex characters in the word are literal.
+    assert.deepEqual(await names('^ze+d'), [])
+  })
 })