feat: opt-in Journal search page and JournalSearchBox

- journal.routes.search (off by default) registers journal-search, the
  results page for ?q= in the API's relevance order (no sort is sent),
  server-rendered with a Polish-aware result count.
- JournalSearchBox: an icon button and a WAI-ARIA combobox with debounced
  ?fields=suggest suggestions, stale answers dropped, query words marked
  ignoring diacritics; a plain GET form without JS.
- The module keeps the search path out of the route cache and the sitemap
  and marks it noindex, follow.
- Client: suggestPosts and the fields option; useJournalLinks.searchLink.

tests/client.test.ts

@@ -183,3 +183,38 @@ test('getAuthor and listAuthorPosts encode the author and map 404 to null', asyn
   assert.equal(await client.getAuthor('nobody'), null)
   assert.equal(await client.listAuthorPosts('nobody'), null)
 })
+
+test('buildPostListQuery passes fields through only when set', () => {
+  assert.deepEqual(buildPostListQuery({ search: 'kurki', fields: 'suggest', perPage: 5 }), {
+    per_page: 5,
+    search: 'kurki',
+    fields: 'suggest',
+  })
+  assert.equal('fields' in buildPostListQuery({ search: 'kurki' }), false)
+})
+
+test('suggestPosts sends search, fields=suggest and per_page, no sort, with the signal', async () => {
+  const page = { data: [{ id: 1, title: 'Kurki', slug: 'kurki', excerpt: 'x', featured_image_url: null, published_at: null }], meta: { current_page: 1, last_page: 1, per_page: 5, total: 1 } }
+  const inits: unknown[] = []
+  const calls: Call[] = []
+  const fetcher = async (path: string, query?: Record<string, string | number>, init?: { signal?: AbortSignal }) => {
+    calls.push({ path, query })
+    inits.push(init)
+    return page
+  }
+  const signal = new AbortController().signal
+  const client = createJournalClient(fetcher)
+  assert.deepEqual(await client.suggestPosts('  kurki ', { signal }), page)
+  assert.deepEqual(calls[0], { path: '/posts', query: { per_page: 5, search: 'kurki', fields: 'suggest' } })
+  assert.equal((inits[0] as { signal: AbortSignal }).signal, signal)
+  await client.suggestPosts('kurki', { perPage: 99 })
+  assert.equal(calls[1]!.query!.per_page, JOURNAL_MAX_PER_PAGE)
+})
+
+test('suggestPosts sends nothing for a term under 3 characters', async () => {
+  const { fetcher, calls } = fakeFetcher({})
+  const res = await createJournalClient(fetcher).suggestPosts('ąę')
+  assert.equal(calls.length, 0)
+  assert.deepEqual(res.data, [])
+  assert.equal(res.meta.total, 0)
+})