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/fayette/index.md

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

data/jurisdictions/us/states/ia/counties/fayette/municipalities/fayette/people/nathan-post.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Nathan Post"
+description: "Mayor, Fayette, IA"
+role: "Mayor, Fayette, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "437e1270-c063-4ac2-bd9c-98da036dc9fe"
+  office: "80104070-5a73-4513-b8ee-a09a6d1ae700"
+  tenure: "08117de6-865f-4e39-9963-9a5e329d386d"
+  jurisdiction: "609712ee-8fee-42f8-9cfa-0b34b1dbd3e0"
+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"
+---
+
+# Nathan Post
+
+Current Mayor, Fayette, 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/fayette/municipalities/oelwein/people/brett-devore.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Brett DeVore"
+description: "Mayor, Oelwein, IA"
+role: "Mayor, Oelwein, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2023-01-01"
+  current: true
+ids:
+  person: "b38ac920-8c1f-4214-94b0-c1e25351faa4"
+  office: "c65d0a9f-f5da-469b-a349-1bfeab49005b"
+  tenure: "2291595d-0584-47cd-a699-79e1a282df4f"
+  jurisdiction: "c8659ed4-e35c-4550-a078-5854314a56c8"
+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"
+---
+
+# Brett DeVore
+
+Current Mayor, Oelwein, IA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).