chore: remove four modules nothing in the app uses (#1403)

* chore: remove four modules nothing in the app uses

src/app/sourceSlot.js re-exported src/sources/sourceSlot.js, which every
caller imports directly. src/data/flowTiles.js and src/data/issPass.js were
reached only by their own tests. src/data/localGeojson.js wrapped
localGeojsonCore.js with the app's services, which the catalog already
passes itself. The local GeoJSON layer tests now build layers the way the
catalog does, so they keep covering localGeojsonCore.js; only the test of
the wrapper's own default host goes. Boundary lists, format scope and docs
drop the removed paths.

* docs: changelog for #1403

docs/CURRENT-STATE.md

@@ -4662,7 +4662,7 @@ current route throughout enabling, enabled, disabling, and uncertain lifecycle
 renders. Both routes preserve Radio power, playback, station, filter, and volume
 state.
 
-Bundled datasets live in `src/data/local_data/` with per-folder provenance READMEs; they are lazily loaded via `src/data/localGeojson.js` (Vite `?url` assets) when toggled on.
+Bundled datasets live in `src/data/local_data/` with per-folder provenance READMEs; they are lazily loaded via `src/data/localGeojsonCore.js` (Vite `?url` assets) when toggled on.
 
 A bundled dataset that fails to load is a broken install, not a blip, so it is
 never swallowed: `localGeojson.js` guards `response.ok`, reports `error` +