Sync: officeholders v3 — fresh export from live Atlas DB (13,329 tenures)

Re-exported directly from Postgres (10.0.0.116), not Atlas's introspection,
which under-reported the roster (its v3 export had 11,473, missing the
restored Florida League of Cities municipal set). Live DB current tenures:
state 7,561 · municipal 4,009 · county 1,217 · federal 542.

- build.py now reads officeholders-v3.jsonl (was v2); dataset vintage 2026-07-04
- fixed one corrupt start_date at source-export (21021-12-03 -> 2021-12-03,
  Lorraine Borowski, Mayor of Decorah IA)
- scripts/build_viz.py: committed, deterministic generator for the Board's
  county_data.json / county_detail.json (previously built ad-hoc)
- generate_changelog.py: ignore files whose only change is the vintage stamp,
  so the diff reflects government change, not re-export bookkeeping

Person files 11,285 -> 13,329. Non-FL municipal officials (1,903) are in the
tree but not yet county-mappable (place->county crosswalk still NULL).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

data/jurisdictions/us/states/fl/counties/jackson/people/michael-m-j-jackson.md

@@ -0,0 +1,39 @@
+---
+type: Person
+title: "Michael \"M.J.\" Jackson"
+description: "Jackson County School Board — Jackson County, FL"
+role: "Jackson County School Board"
+level: "county"
+branch: "legislative"
+state: "FL"
+tenure:
+  start: "2025-01-01"
+  current: true
+ids:
+  person: "5e94baf9-f604-4d6e-b0ee-ba4e88bb15bb"
+  office: "8c7a6dd3-fe10-4769-84c2-bec1fadff0be"
+  tenure: "9ee6936b-dbfe-477a-a0f6-d7bfdf6d5fff"
+  jurisdiction: "347f6a3c-437e-403c-96d2-f4bf97664634"
+sources:
+  - field: office
+    source: "FL Division of Elections"
+  - field: tenure
+    source: "FL Division of Elections"
+  - field: jurisdiction
+    source: "Census TIGER 2024"
+confidence: official
+tags: [officeholder, county, legislative, fl]
+timestamp: "2026-07-04"
+---
+
+# Michael "M.J." Jackson
+
+Current Jackson County School Board (Jackson County, FL).
+
+## Sources
+
+- office: FL Division of Elections
+- tenure: FL Division of Elections
+- jurisdiction: Census TIGER 2024
+
+Generated from the Atlas officeholders v3 export (2026-07-04).