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/davis/index.md

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

data/jurisdictions/us/states/ia/counties/davis/municipalities/bloomfield/people/chris-miller.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Chris Miller"
+description: "Mayor, Bloomfield, IA"
+role: "Mayor, Bloomfield, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "68b1d3ed-375f-4c0a-a9c6-867d8fec69b0"
+  office: "ba462dee-8abc-4f4d-bcfa-934aefd0c8d9"
+  tenure: "13f6730c-a66a-4b8a-9bc8-fdb04d7bdb5c"
+  jurisdiction: "f261e85c-6200-474f-93ab-79ee1373c9b3"
+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"
+---
+
+# Chris Miller
+
+Current Mayor, Bloomfield, 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/davis/municipalities/drakesville/people/bob-sampson.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Bob Sampson"
+description: "Mayor, Drakesville, IA"
+role: "Mayor, Drakesville, IA"
+level: "municipal"
+branch: "executive"
+state: "IA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "52a44517-9167-4c70-96a2-bcb208487a1e"
+  office: "1d66a471-95f1-40d3-9bd9-86f59f7521d7"
+  tenure: "1d96ea38-f990-4ae3-9a78-65325c179913"
+  jurisdiction: "49c802d4-01ef-43ab-9c28-d0b8461183d5"
+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"
+---
+
+# Bob Sampson
+
+Current Mayor, Drakesville, IA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).