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/chickasaw/index.md

@@ -32,7 +32,7 @@ timestamp: "2026-07-03"
 
 # Chickasaw County, IA
 
-County jurisdiction.
+County jurisdiction — 2 officeholders mapped.
 
 ## Demographics (ACS 2023)
 

data/jurisdictions/us/states/ia/counties/chickasaw/municipalities/nashua/people/alex-anthofer.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Alex Anthofer"
+description: "Mayor, Nashua, IA"
+role: "Mayor, Nashua, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "2680dbfe-6d2e-47ef-89e6-1847377a37d4"
+  office: "6a23ce0b-ae46-4497-b171-0b659efa78cb"
+  tenure: "538450dd-2bee-4c66-a39f-61e22836c4a0"
+  jurisdiction: "c3d13dcd-9625-4d5f-bbf7-9d3a69b5db4e"
+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"
+---
+
+# Alex Anthofer
+
+Current Mayor, Nashua, IA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).

data/jurisdictions/us/states/ia/counties/chickasaw/municipalities/new-hampton/people/steven-geerts.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Steven Geerts"
+description: "Mayor, New Hampton, IA"
+role: "Mayor, New Hampton, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "bd58ad68-ef94-4644-85ea-5875adce9327"
+  office: "025842e0-12be-4fc9-a69a-1b169796b043"
+  tenure: "cb3a0f65-f98d-4277-93b0-35f980f0969b"
+  jurisdiction: "3f51eb36-3489-43fe-956a-b292a084a24b"
+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"
+---
+
+# Steven Geerts
+
+Current Mayor, New Hampton, IA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).