Add editorial city copy for 83 city/record pages, wired through payload + templates

Introduce backend/city_copy.json: original, researched per-city editorial copy
(a lede, 2-4 body paragraphs, and a records-page intro), keyed by slug next to
the existing Wikipedia cities_flavor.json. Covers 83 of the 90 cities that had
no flavor blurb at all; each entry carries the independent sources it was
written from and reviewed:false pending a human spot-check.

Wire it end to end:
- cities.copy(slug) loader, mirroring cities.flavor() (lazy, tolerant of a
  missing file so pages render fine until copy exists).
- A `copy` field on the city and records content payloads. PAYLOAD_VER p2->p3
  so cached content rows rebuild with the new field instead of serving the old
  shape.
- city.html.j2 renders the editorial lede + body in place of the Wikipedia
  blurb, falling back to the flavor blurb (with its "via Wikipedia" credit)
  wherever copy isn't written yet. records.html.j2 gains a per-city intro line
  it never had before.

Additive and backward-compatible: no API contract bump, and any slug without a
copy entry keeps its existing behavior.

backend/api/content_payloads.py

@@ -202,6 +202,7 @@ def city_payload(request_origin: str, base: str, city: dict, history, recent=Non
     records = grading.all_time_records(history)
     unit = unit_for_country(city.get("country_code"))
     flavor = cities.flavor(city["slug"])
+    copy = cities.copy(city["slug"])
     event = city_events.get(city["slug"])
     today = _today_vs_normal_raw(history, recent) if recent is not None else None
 
@@ -238,7 +239,7 @@ def city_payload(request_origin: str, base: str, city: dict, history, recent=Non
         "wettest_month_slug": wettest["slug"] if wettest else None,
         "all_time_records": records,
         "today_vs_normal": today,
-        "flavor": flavor, "event": event, "default_unit": unit,
+        "flavor": flavor, "copy": copy, "event": event, "default_unit": unit,
         "breadcrumb": breadcrumb,
         "canonical_path": f"/climate/{city['slug']}",
         "page_title": _titled(f"{title} climate: daily normals, records & how unusual it is now"),
@@ -328,6 +329,7 @@ def records_payload(request_origin: str, base: str, city: dict, history) -> dict
     lo_rec = (rec.get("tmin") or {}).get("min")
     lo_date = (rec.get("tmin") or {}).get("min_date")
     unit = unit_for_country(city.get("country_code"))
+    copy = cities.copy(city["slug"])
 
     rows = []
     for key, label in METRIC_LABELS:
@@ -374,7 +376,7 @@ def records_payload(request_origin: str, base: str, city: dict, history) -> dict
     }
     return {
         "year_range": year_range, "n_years": n_years,
-        "rows": rows,
+        "rows": rows, "copy": copy,
         "all_time_records": rec,
         "monthly": _monthly_records_raw(history),
         "seasonal": _seasonal_records_raw(history, city["lat"]),

backend/api/payloads.py

@@ -26,7 +26,8 @@ OBS_COLS = ("tmax", "tmin", "precip", "feels", "humid", "wind", "gust")
 # The version is part of every derived-store validity token, so one bump
 # atomically orphans all pre-upgrade cached payloads instead of letting a stale
 # row whose history_end happens to match keep serving the old shape.
-PAYLOAD_VER = "p2"   # p2: place labels now carry the trailing country component
+PAYLOAD_VER = "p3"   # p3: content-city/records payloads carry an editorial `copy` field
+                     # p2: place labels now carry the trailing country component
 
 CAL_MAX_SPAN_DAYS = 732  # ~2 years — the most a single calendar request will grade
                          # (the frontend splits longer spans into 2-year chunks)

backend/data/cities.py

@@ -7,9 +7,11 @@ import paths
 
 _PATH = paths.CITIES_JSON
 _FLAVOR_PATH = paths.CITIES_FLAVOR_JSON
+_COPY_PATH = paths.CITY_COPY_JSON
 _CITIES: list[dict] | None = None
 _BY_SLUG: dict[str, dict] | None = None
 _FLAVOR: dict[str, dict] | None = None
+_COPY: dict[str, dict] | None = None
 _DUPES: dict[str, dict[str, int]] | None = None
 
 
@@ -49,6 +51,21 @@ def flavor(slug: str) -> dict | None:
     return _FLAVOR.get(slug)
 
 
+def copy(slug: str) -> dict | None:
+    """A city's editorial copy {lede, body, records_intro, sources, ...} from
+    city_copy.json, or None when it hasn't been written yet (the page falls back
+    to the Wikipedia flavor blurb). Mirrors flavor() — lazy, tolerant of a
+    missing/malformed file."""
+    global _COPY
+    if _COPY is None:
+        try:
+            with open(_COPY_PATH, encoding="utf-8") as f:
+                _COPY = json.load(f)
+        except (OSError, ValueError):
+            _COPY = {}
+    return _COPY.get(slug)
+
+
 def title_name(city: dict) -> str:
     """The shortest label that still names this city unambiguously — for page
     titles, where display_name()'s region + country spend the width Google gives

backend/paths.py

@@ -27,3 +27,4 @@ LOGS_DIR = os.environ.get("THERMOGRAPH_LOGS_DIR") or os.path.join(REPO_DIR, "log
 # gen_flavor), not runtime state — hence at the repo root, not data/.
 CITIES_JSON = os.path.join(REPO_DIR, "cities.json")
 CITIES_FLAVOR_JSON = os.path.join(REPO_DIR, "cities_flavor.json")
+CITY_COPY_JSON = os.path.join(REPO_DIR, "city_copy.json")

frontend/content.py

@@ -198,7 +198,7 @@ def city_page(request: Request, slug: str) -> Response:
             "months": months, "warmest": warmest, "coldest": coldest, "wettest": wettest,
             "records": records, "today": today,
             "tool_hash": f"{j['city']['lat']:.5f},{j['city']['lon']:.5f}",
-            "flavor": j["flavor"], "event": j["event"],
+            "flavor": j["flavor"], "copy": j.get("copy"), "event": j["event"],
             "compare_url": f"{BASE}/compare#loc={j['city']['lat']:.4f},{j['city']['lon']:.4f}",
             "breadcrumb": _breadcrumb_tuples(j["breadcrumb"]),
             "canonical_path": j["canonical_path"],
@@ -307,6 +307,7 @@ def records_page(request: Request, slug: str) -> Response:
             "section": "climate", "city": city, "display": j.get("display", city["name"]), "name": city["name"],
             "year_range": j["year_range"], "n_years": j["n_years"],
             "rows": rows, "monthly": monthly, "seasonal": seasonal,
+            "copy": j.get("copy"),
             "hemisphere": j["hemisphere"], "all_time": j["all_time_records"],
             "canonical_path": j["canonical_path"],
             "breadcrumb": _breadcrumb_tuples(j["breadcrumb"]),

frontend/templates/city.html.j2

@@ -16,7 +16,11 @@
      <b>{{ warmest.name }}</b>, averaging a high of {{ warmest.high }}, and its coldest is
      <b>{{ coldest.name }}</b>, with an average low of {{ coldest.low }}.{% endif %}</p>
 
-  {% if flavor %}
+  {% if copy and copy.lede %}
+  <p class="city-blurb">{{ copy.lede }}</p>
+  {% for para in copy.body %}<p class="city-body">{{ para }}</p>
+  {% endfor %}
+  {% elif flavor %}
   <p class="city-blurb">{{ flavor.extract }}{% if flavor.url %}
     <a class="blurb-src" href="{{ flavor.url }}" rel="nofollow">via Wikipedia</a>{% endif %}</p>
   {% endif %}

frontend/templates/records.html.j2

@@ -24,6 +24,7 @@
      climate history.{% if all_time.tmax and all_time.tmin %} Its hottest day on record reached
      {{ temp(all_time.tmax.max) }} on {{ all_time.tmax.max_date }}; its coldest fell to
      {{ temp(all_time.tmin.min) }} on {{ all_time.tmin.min_date }}.{% endif %}</p>
+  {% if copy and copy.records_intro %}<p class="records-intro">{{ copy.records_intro }}</p>{% endif %}
 
   <section class="climate-records-section">
     <h2>Records by month</h2>