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/ca/counties/imperial/index.md

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

data/jurisdictions/us/states/ca/counties/imperial/municipalities/el-centro/people/tomas-olivia.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Tomas Olivia"
+description: "Mayor, El Centro, CA"
+role: "Mayor, El Centro, CA"
+level: "municipal"
+branch: "executive"
+state: "CA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "c440dca5-32c3-4631-86f3-048af0a67284"
+  office: "6b113d73-3dba-4af2-85b0-188f958b99a9"
+  tenure: "4e8c5ebe-4057-491a-96af-1ade34460798"
+  jurisdiction: "ec73750e-ac79-42df-a70a-01dbd92e7e8e"
+sources:
+  - field: office
+    source: "Wikidata"
+  - field: tenure
+    source: "Wikidata"
+  - field: jurisdiction
+    source: "Census TIGER 2024"
+confidence: official
+tags: [officeholder, municipal, executive, ca]
+timestamp: "2026-07-04"
+---
+
+# Tomas Olivia
+
+Current Mayor, El Centro, CA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).

data/jurisdictions/us/states/ca/counties/imperial/municipalities/imperial/people/geoffrey-dale.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Geoffrey Dale"
+description: "Mayor, Imperial, CA"
+role: "Mayor, Imperial, CA"
+level: "municipal"
+branch: "executive"
+state: "CA"
+tenure:
+  start: "2026-06-20"
+  current: true
+ids:
+  person: "3421647e-5a87-4e3f-8284-5cf33dcfd79f"
+  office: "daa55b36-6a9f-4562-9452-534e81631831"
+  tenure: "4fe3f98c-50e8-4e1c-aade-52a7fb299d34"
+  jurisdiction: "36b9996e-b28b-4e54-b042-db125eec128d"
+sources:
+  - field: office
+    source: "Wikidata"
+  - field: tenure
+    source: "Wikidata"
+  - field: jurisdiction
+    source: "Census TIGER 2024"
+confidence: official
+tags: [officeholder, municipal, executive, ca]
+timestamp: "2026-07-04"
+---
+
+# Geoffrey Dale
+
+Current Mayor, Imperial, CA.
+
+## Sources
+
+- office: Wikidata
+- tenure: Wikidata
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).