Municipals: nest 1,823 city officeholders under their real counties

Pull Atlas's place→county crosswalk (Census TIGER 2024 places × county
geometries, 32,041 places) into the build as a committed raw input, and
use it to resolve municipal officeholders whose county was unknown.

- data/place_county_crosswalk.jsonl — new raw input (place_geoid → county_geoid)
- build.py — place-name+state → county_geoid → ACS county slug as a fallback
  in county_slug(); city_slug() generalized to non-FL bare place labels
- data/sources/sources.yaml — provenance entry for the crosswalk

_unresolved municipals: 1919 → 58. The remainder are genuine: CT planning
regions (post-county), county-level rows mislabeled municipal upstream,
consolidated city-counties (null label), Wikidata-QID placeholder names,
and ambiguous same-name places — left unresolved rather than guessed.

Join key is county_geoid (5-digit FIPS); the directory slug is taken from
the ACS county node so municipals nest under the exact existing county dir.
Deterministic (byte-identical rebuild); validate.py passes 19,721 records.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

data/jurisdictions/us/states/ia/counties/polk/municipalities/johnston/people/paula-dierenfeld.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Paula Dierenfeld"
+description: "Mayor, Johnston, IA"
+role: "Mayor, Johnston, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2008-01-01"
+  current: true
+ids:
+  person: "e89db294-c471-46e7-905a-14f4a0cc8417"
+  office: "3becc1a7-0d64-4390-9b87-f6b50c0fca71"
+  tenure: "2308ee17-8565-44d7-ae90-a839d87168b4"
+  jurisdiction: "e1d069d5-6b0c-45f1-b17e-f83510dd848a"
+sources:
+  - field: office
+    source: "Wikidata"
+  - field: tenure
+    source: "Wikidata"
+  - field: jurisdiction
+    source: "Census TIGER 2024"
+confidence: official
+tags: [officeholder, municipal, executive, ia]
+timestamp: "2026-07-04"
+---
+
+# Paula Dierenfeld
+
+Current Mayor, Johnston, IA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).