Add elections + demographics layer: candidates and jurisdictions

Two new entity types, built deterministically from the raw exports:

  Candidate (2,494)     — 2026 federal candidates as files under
                          us/states/<st>/candidates/, with office,
                          district, party, incumbent/challenger stance,
                          campaign committee, FEC id.

  Jurisdiction (3,494)  — demographic nodes carrying ACS 2023 data:
                          3,131 counties (deduped from 3,231 mixed-format
                          fips keys) + 363 congressional districts.

This completes the county skeleton nationwide: every US county is now a
browsable node with population, income, poverty, race, education and
housing — even where no officeholders are mapped yet. In Florida the
county index.md merges into the existing dir and reports its officeholder
count alongside demographics (St. Lucie: 33 officeholders + ACS profile).

build.py now reads seven raw inputs in one deterministic pass
(byte-identical on rerun). The mirror now answers: who holds power, who
runs this institution, who is running, and what each place is made of.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

data/jurisdictions/us/states/me/districts/01.md

@@ -0,0 +1,59 @@
+---
+type: Jurisdiction
+title: "ME-01"
+classification: congressional-district
+state: "ME"
+district: "ME-01"
+demographics:
+  population: 707732
+  population_under_18: 138413
+  population_18_64: 221324
+  population_65_plus: 347995
+  median_household_income: 90131
+  poverty_rate: 8.25
+  homeownership_rate: 72.56
+  unemployment_rate: 2.74
+  median_home_value: 448800
+  gini_index: 0.4525
+  vacancy_rate: 16.3
+  race_white: 626345
+  race_black: 15455
+  race_asian: 12107
+  hispanic: 18367
+  bachelors_plus: 242530
+sources:
+  - field: demographics
+    source: Census ACS 2023
+confidence: official
+tags: [jurisdiction, congressional-district, me]
+timestamp: "2026-07-03"
+---
+
+# ME-01
+
+Congressional district ME-01.
+
+## Demographics (ACS 2023)
+
+| Measure | Value |
+| --- | --- |
+| Population | 707732 |
+| Under 18 | 138413 |
+| 18–64 | 221324 |
+| 65+ | 347995 |
+| Median household income | 90131 |
+| Poverty rate | 8.25 |
+| Homeownership rate | 72.56 |
+| Unemployment rate | 2.74 |
+| Median home value | 448800 |
+| Gini index | 0.4525 |
+| Vacancy rate | 16.3 |
+| White | 626345 |
+| Black | 15455 |
+| Asian | 12107 |
+| Hispanic/Latino | 18367 |
+| Bachelor's or higher | 242530 |
+
+## Source
+
+- demographics: Census ACS 2023

data/jurisdictions/us/states/me/districts/02.md

@@ -0,0 +1,59 @@
+---
+type: Jurisdiction
+title: "ME-02"
+classification: congressional-district
+state: "ME"
+district: "ME-02"
+demographics:
+  population: 697280
+  population_under_18: 140825
+  population_18_64: 203644
+  population_65_plus: 352811
+  median_household_income: 67291
+  poverty_rate: 13.0
+  homeownership_rate: 74.09
+  unemployment_rate: 2.71
+  median_home_value: 255500
+  gini_index: 0.4462
+  vacancy_rate: 22.58
+  race_white: 633693
+  race_black: 13790
+  race_asian: 6687
+  hispanic: 14502
+  bachelors_plus: 147082
+sources:
+  - field: demographics
+    source: Census ACS 2023
+confidence: official
+tags: [jurisdiction, congressional-district, me]
+timestamp: "2026-07-03"
+---
+
+# ME-02
+
+Congressional district ME-02.
+
+## Demographics (ACS 2023)
+
+| Measure | Value |
+| --- | --- |
+| Population | 697280 |
+| Under 18 | 140825 |
+| 18–64 | 203644 |
+| 65+ | 352811 |
+| Median household income | 67291 |
+| Poverty rate | 13.0 |
+| Homeownership rate | 74.09 |
+| Unemployment rate | 2.71 |
+| Median home value | 255500 |
+| Gini index | 0.4462 |
+| Vacancy rate | 22.58 |
+| White | 633693 |
+| Black | 13790 |
+| Asian | 6687 |
+| Hispanic/Latino | 14502 |
+| Bachelor's or higher | 147082 |
+
+## Source
+
+- demographics: Census ACS 2023