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/ri/districts/01.md

@@ -0,0 +1,59 @@
+---
+type: Jurisdiction
+title: "RI-01"
+classification: congressional-district
+state: "RI"
+district: "RI-01"
+demographics:
+  population: 555745
+  population_under_18: 119221
+  population_18_64: 193055
+  population_65_plus: 243469
+  median_household_income: 77683
+  poverty_rate: 12.46
+  homeownership_rate: 59.11
+  unemployment_rate: 4.41
+  median_home_value: 464100
+  gini_index: 0.4694
+  vacancy_rate: 5.6
+  race_white: 357055
+  race_black: 36339
+  race_asian: 22124
+  hispanic: 113918
+  bachelors_plus: 153327
+sources:
+  - field: demographics
+    source: Census ACS 2023
+confidence: official
+tags: [jurisdiction, congressional-district, ri]
+timestamp: "2026-07-03"
+---
+
+# RI-01
+
+Congressional district RI-01.
+
+## Demographics (ACS 2023)
+
+| Measure | Value |
+| --- | --- |
+| Population | 555745 |
+| Under 18 | 119221 |
+| 18–64 | 193055 |
+| 65+ | 243469 |
+| Median household income | 77683 |
+| Poverty rate | 12.46 |
+| Homeownership rate | 59.11 |
+| Unemployment rate | 4.41 |
+| Median home value | 464100 |
+| Gini index | 0.4694 |
+| Vacancy rate | 5.6 |
+| White | 357055 |
+| Black | 36339 |
+| Asian | 22124 |
+| Hispanic/Latino | 113918 |
+| Bachelor's or higher | 153327 |
+
+## Source
+
+- demographics: Census ACS 2023

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

@@ -0,0 +1,59 @@
+---
+type: Jurisdiction
+title: "RI-02"
+classification: congressional-district
+state: "RI"
+district: "RI-02"
+demographics:
+  population: 556563
+  population_under_18: 120107
+  population_18_64: 182682
+  population_65_plus: 253774
+  median_household_income: 92127
+  poverty_rate: 11.87
+  homeownership_rate: 68.01
+  unemployment_rate: 5.66
+  median_home_value: 448500
+  gini_index: 0.4708
+  vacancy_rate: 10.6
+  race_white: 405305
+  race_black: 25425
+  race_asian: 19631
+  hispanic: 95058
+  bachelors_plus: 157555
+sources:
+  - field: demographics
+    source: Census ACS 2023
+confidence: official
+tags: [jurisdiction, congressional-district, ri]
+timestamp: "2026-07-03"
+---
+
+# RI-02
+
+Congressional district RI-02.
+
+## Demographics (ACS 2023)
+
+| Measure | Value |
+| --- | --- |
+| Population | 556563 |
+| Under 18 | 120107 |
+| 18–64 | 182682 |
+| 65+ | 253774 |
+| Median household income | 92127 |
+| Poverty rate | 11.87 |
+| Homeownership rate | 68.01 |
+| Unemployment rate | 5.66 |
+| Median home value | 448500 |
+| Gini index | 0.4708 |
+| Vacancy rate | 10.6 |
+| White | 405305 |
+| Black | 25425 |
+| Asian | 19631 |
+| Hispanic/Latino | 95058 |
+| Bachelor's or higher | 157555 |
+
+## Source
+
+- demographics: Census ACS 2023