enforce coding style: type over interface, camelCase, FilterLookup type

- Replace `interface` with `type` for RegionData and LoadedMapState
- Rename snake_case variables to camelCase in processors/helpers.ts
- Extract FilterLookup type from ValidFilterLookup class to avoid
  private-member nominal type errors across Vue component boundaries
- Add coding style section to CLAUDE.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: trbKnl

src/App.vue

@@ -125,7 +125,7 @@ import { Processor } from "./processors/processor"
 import { mapConfigs } from "./config/loader"
 import type { MapConfig } from "./config/types"
 import { MapManager } from "./mapManager"
-import type { ValidFilterLookup } from "./mapManager"
+import type { FilterLookup } from "./mapManager"
 
 // UI toggles
 const showInfo = ref(false)
@@ -140,7 +140,7 @@ const regionData = ref<RegionData[] | undefined>(undefined)
 const selectedLegendColor = ref<string>("")
 const config = ref<MapConfig | undefined>(undefined)
 const configs = ref<MapConfig[]>([])
-const validFilterLookup = ref<ValidFilterLookup | undefined>(undefined)
+const validFilterLookup = ref<FilterLookup | undefined>(undefined)
 
 
 // Filter state

src/components/control-panel.vue

@@ -131,15 +131,15 @@ import Checkbox from './checkbox.vue'
 import InputField from './input-field.vue'
 import { colorSchemes } from '../config/types.ts'
 import type { MapConfig } from '../config/types.ts'
-import type { ValidFilterLookup } from '../mapManager.ts'
+import type { FilterLookup } from '../mapManager.ts'
 
 const schemeNames: string[] = [...colorSchemes]
 
 const props = defineProps<{
   availableFilterOptions?: Record<string, any>
   config?: MapConfig
   loading?: boolean
-  validFilterLookup?: ValidFilterLookup
+  validFilterLookup?: FilterLookup
 }>()
 
 const emit = defineEmits([

src/mapManager.ts

@@ -5,13 +5,17 @@ import { Processor } from "./processors/processor"
 import type { MapConfig } from "./config/types"
 import { fetchPublicFile } from "./helpers"
 
-export interface LoadedMapState {
+export type FilterLookup = {
+  lookup(knownValues: Record<string, string>, targetKey: string): string[]
+}
+
+export type LoadedMapState = {
   geojsonData: GeoJSON
   dataProcessor: Processor
   regionData: RegionData[]
   availableFilterOptions: { [key: string]: string[] }
   selectedFilters: { [key: string]: string }
-  validFilterLookup: ValidFilterLookup
+  validFilterLookup: FilterLookup
 }
 
 type MapKey = string

src/processors/helpers.ts

@@ -60,11 +60,11 @@ export async function getRegionData(
   datasetName: string
 ): Promise<RegionData[]> {
 
-  const filter_clause = Object.entries(selectedCategoryValues)
-    .map(([category_col, value]) =>
+  const filterClause = Object.entries(selectedCategoryValues)
+    .map(([categoryCol, value]) =>
       value === MISSING_LABEL
-        ? `${category_col} IS NULL`
-        : `${category_col} = '${value}'`
+        ? `${categoryCol} IS NULL`
+        : `${categoryCol} = '${value}'`
     )
     .join(" AND ")
 
@@ -75,7 +75,7 @@ export async function getRegionData(
     FROM
       ${readFunction}('${datasetName}')
     WHERE
-      ${filter_clause}
+      ${filterClause}
   `
   const out = await executeQuery(query) as RegionData[]
   return out

src/processors/types.ts

@@ -1,4 +1,4 @@
-export interface RegionData {
+export type RegionData = {
   regionId: string
   value: number
 }