feat(suggest): Typesense rows for autosuggest, no DataFrame

search_schools_typesense returns URNs, which forces the caller to
hydrate from the 25,000-row in-memory frame. Every field a suggestion
needs is already in the Typesense document, so this returns documents
and the caller needs no pandas at all — the difference between a query
that can run per keystroke and one that cannot.

Never raises. Typesense unreachable or erroring gives an empty list,
because a dropdown that quietly stops appearing is the right failure for
a keystroke path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015mWQnpye9F299NVRCCSRvj

backend/tests/test_suggest.py

@@ -0,0 +1,71 @@
+"""Tests for school autosuggest (spec 2026-08-26)."""
+
+from backend import data_loader
+
+
+class _FakeDocs:
+    def __init__(self, hits, explode=False):
+        self._hits = hits
+        self._explode = explode
+        self.last_params = None
+
+    def search(self, params):
+        self.last_params = params
+        if self._explode:
+            raise RuntimeError("typesense is down")
+        return {"hits": [{"document": d} for d in self._hits]}
+
+
+class _FakeClient:
+    def __init__(self, hits, explode=False):
+        self.docs = _FakeDocs(hits, explode)
+        self.collections = {"schools": type("C", (), {"documents": self.docs})()}
+
+
+_HIT = {
+    "urn": 100010, "school_name": "Brecknock Primary School",
+    "local_authority": "Camden", "postcode": "NW1 1AA",
+    "phase": "Primary", "school_type": "Community school",
+}
+
+
+def _use(monkeypatch, client):
+    monkeypatch.setattr(data_loader, "_get_typesense_client", lambda: client)
+
+
+def test_returns_the_fields_a_suggestion_needs(monkeypatch):
+    # Local authority is not decoration: there are many schools called
+    # "St Mary's", and a list without it cannot be chosen between.
+    _use(monkeypatch, _FakeClient([_HIT]))
+    out = data_loader.suggest_schools_typesense("breck")
+    assert out == [{
+        "urn": 100010, "school_name": "Brecknock Primary School",
+        "local_authority": "Camden", "postcode": "NW1 1AA",
+        "phase": "Primary", "school_type": "Community school",
+    }]
+
+
+def test_a_missing_optional_field_becomes_an_empty_string(monkeypatch):
+    # phase and school_type are optional in the Typesense schema. A missing
+    # key must not KeyError in the keystroke path.
+    _use(monkeypatch, _FakeClient([{"urn": 1, "school_name": "X",
+                                    "local_authority": "Y", "postcode": "Z"}]))
+    out = data_loader.suggest_schools_typesense("x")
+    assert out[0]["phase"] == "" and out[0]["school_type"] == ""
+
+
+def test_typesense_unavailable_gives_no_suggestions_rather_than_raising(monkeypatch):
+    _use(monkeypatch, None)
+    assert data_loader.suggest_schools_typesense("anything") == []
+
+
+def test_a_typesense_error_gives_no_suggestions_rather_than_raising(monkeypatch):
+    _use(monkeypatch, _FakeClient([], explode=True))
+    assert data_loader.suggest_schools_typesense("anything") == []
+
+
+def test_the_limit_is_passed_through_and_clamped(monkeypatch):
+    client = _FakeClient([])
+    _use(monkeypatch, client)
+    data_loader.suggest_schools_typesense("x", limit=500)
+    assert client.docs.last_params["per_page"] == 20