fix: make regional time series discoverable

frontend/README.md

@@ -6,7 +6,7 @@ The persisted `Kempen Regional Workbench` is the automatic operational data cont
 
 The user-facing shell is task based: `Kaart`, `Bronnen`, `Kwaliteit`, `Beeldanalyse`, `Downloads`, `Status` and `Beheer`. Internal benchmark projects, raw dataset metadata, provider capabilities, model registry details and QA evidence remain accessible through labelled advanced disclosures instead of competing with the normal workflow.
 
-Detection defaults to the configured local YOLO asset and automatically selects an available raster and active model asset where possible. The model registry and preflight remain honest when PyTorch, Ultralytics, a local model file or a tile manifest is unavailable. The active building profile is operational but remains review-required: its recorded coverage-aware benchmark is approximately precision 0.590, recall 0.577 and F1 0.582 over seven positive AOIs, with zero detections in the empty-background control. Another training pass is intentionally blocked until the generated false-positive and false-negative review decisions are completed.
+Detection defaults to the configured local YOLO asset and automatically selects an available raster and active model asset where possible. The model registry and preflight remain honest when PyTorch, Ultralytics, a local model file or a tile manifest is unavailable. The active building profile is operational but remains review-required: its current coverage-aligned benchmark is approximately precision 0.614, recall 0.606 and F1 0.607 over seven positive AOIs, with zero detections in all three pure-empty controls. A reviewed challenger remains inactive because it produced two detections in empty Postel forest.
 
 Map-driven building analysis uses the documented footprint-IoU `0.25` and
 distinguishes model candidates from verified buildings. It shows persisted
@@ -20,6 +20,10 @@ current, while `Evolution` lets the operator compare an earlier and later
 snapshot from the same series over a drawn rectangle. Results show units,
 absolute/percentage change, estimate status and source limitations.
 Added/removed/modified overlays only appear for stable source identities.
+When Evolution is opened from a current-only theme, the explorer automatically
+switches to the first available persisted series. Theme cards then show either
+the number and range of historical observations or `Alleen huidige toestand`,
+so a single GRB snapshot can no longer strand the workflow in an empty state.
 When a theme has multiple valid methodologies, a compact series selector keeps
 them explicit. Forest therefore defaults to the official modern 2013-2025
 10 m series, while the separate 1778-1969 historical map series remains

frontend/src/components/map/MapWorkspace.tsx

@@ -613,10 +613,15 @@ export function MapWorkspace({
   const activeScopeProject = projects.find((project) => project.id === selectedProjectId) ?? null
   const activeScopeLabel = activeScopeProject ? operationalScopeProjectLabel(activeScopeProject) : 'Werkgebied'
   const municipalityAreaCount = areas.filter((area) => /^Gemeente\s/i.test(area.name)).length
-  const activeTemporalSeriesGroups = useMemo(
-    () => listThemeTemporalSeries(availableMapDatasets, activeTheme),
-    [activeTheme, availableMapDatasets],
+  const themeTemporalSeriesMap = useMemo(
+    () =>
+      Object.fromEntries(
+        DATA_THEMES.map((theme) => [theme.id, listThemeTemporalSeries(availableMapDatasets, theme)]),
+      ) as Record<DataThemeId, TemporalSeriesGroup[]>,
+    [availableMapDatasets],
   )
+  const activeTemporalSeriesGroups = themeTemporalSeriesMap[activeTheme.id]
+  const availableEvolutionThemes = DATA_THEMES.filter((theme) => themeTemporalSeriesMap[theme.id].length > 0)
   const activeTemporalSeriesGroup = activeTemporalSeriesGroups.find((group) => group.key === selectedTemporalSeriesKey)
     ?? activeTemporalSeriesGroups[0]
   const activeTemporalSeries = activeTemporalSeriesGroup?.items ?? EMPTY_TEMPORAL_SERIES
@@ -808,7 +813,10 @@ export function MapWorkspace({
   }
 
   const selectDataTheme = (theme: DataTheme) => {
-    const dataset = themeDatasetMap[theme.id]
+    const temporalGroup = themeTemporalSeriesMap[theme.id][0]
+    const dataset = analysisMode === 'evolution'
+      ? temporalGroup?.items[temporalGroup.items.length - 1] ?? null
+      : themeDatasetMap[theme.id]
     if (!dataset) {
       return
     }
@@ -820,6 +828,16 @@ export function MapWorkspace({
   const setExplorerMode = (mode: 'current' | 'evolution') => {
     setAnalysisMode(mode)
     clearTemporalComparison()
+    if (mode !== 'evolution' || activeTemporalSeriesGroups.length > 0) {
+      return
+    }
+    const fallbackTheme = availableEvolutionThemes[0]
+    const fallbackGroup = fallbackTheme ? themeTemporalSeriesMap[fallbackTheme.id][0] : null
+    const fallbackDataset = fallbackGroup?.items[fallbackGroup.items.length - 1]
+    if (fallbackTheme && fallbackDataset) {
+      setActiveThemeId(fallbackTheme.id)
+      onOpenDatasetInMap(fallbackDataset)
+    }
   }
 
   const loadAllThemeResults = async (bbox: VectorSelectionBBox, areaId?: string) => {
@@ -985,11 +1003,19 @@ export function MapWorkspace({
             <div className="geo-theme-list">
               {DATA_THEMES.map((theme) => {
                 const dataset = themeDatasetMap[theme.id]
+                const temporalGroups = themeTemporalSeriesMap[theme.id]
+                const temporalGroup = temporalGroups[0]
+                const evolutionAvailable = temporalGroups.length > 0
+                const available = Boolean(dataset) && (analysisMode === 'current' || evolutionAvailable)
                 const active = activeThemeId === theme.id
+                const firstObservation = temporalGroup?.items[0]?.observed_at
+                const lastObservation = temporalGroup?.items[temporalGroup.items.length - 1]?.observed_at
+                const firstYear = firstObservation ? new Date(firstObservation).getUTCFullYear() : null
+                const lastYear = lastObservation ? new Date(lastObservation).getUTCFullYear() : null
                 return (
                   <button
                     className={active ? 'geo-theme-option geo-theme-option-active' : 'geo-theme-option'}
-                    disabled={!dataset}
+                    disabled={!available}
                     key={theme.id}
                     type="button"
                     onClick={() => selectDataTheme(theme)}
@@ -998,9 +1024,23 @@ export function MapWorkspace({
                     <span className={`geo-theme-symbol geo-theme-symbol-${theme.id}`} aria-hidden="true" />
                     <span>
                       <strong>{theme.label}</strong>
-                      <small>{dataset ? `${(dataset.feature_count ?? dataset.vector_summary?.feature_count ?? 0).toLocaleString('nl-BE')} objecten beschikbaar` : 'Bron nog niet ingeladen'}</small>
+                      <small>
+                        {analysisMode === 'evolution'
+                          ? evolutionAvailable
+                            ? `${temporalGroup.items.length} meetmomenten${firstYear && lastYear ? ` · ${firstYear}-${lastYear}` : ''}`
+                            : dataset
+                              ? 'Alleen huidige toestand'
+                              : 'Bron nog niet ingeladen'
+                          : dataset
+                            ? `${(dataset.feature_count ?? dataset.vector_summary?.feature_count ?? 0).toLocaleString('nl-BE')} objecten beschikbaar`
+                            : 'Bron nog niet ingeladen'}
+                      </small>
                     </span>
-                    <i>{dataset ? 'Beschikbaar' : 'Ontbreekt'}</i>
+                    <i>
+                      {analysisMode === 'evolution'
+                        ? evolutionAvailable ? 'Tijdreeks' : dataset ? 'Alleen huidig' : 'Ontbreekt'
+                        : dataset ? 'Beschikbaar' : 'Ontbreekt'}
+                    </i>
                   </button>
                 )
               })}
@@ -1012,7 +1052,7 @@ export function MapWorkspace({
                 {analysisOverlayActive
                   ? mapLayerLabel
                   : analysisMode === 'evolution'
-                  ? activeTemporalSeriesGroup?.label ?? 'Geen tijdreeks beschikbaar'
+                  ? activeTemporalSeriesGroup?.label ?? 'Nog geen historische reeks ingeladen'
                   : activeThemeDataset ? getDatasetDisplayName(activeThemeDataset) : 'Geen databron beschikbaar'}
               </strong>
               <small>
@@ -1021,7 +1061,7 @@ export function MapWorkspace({
                   : analysisMode === 'evolution'
                   ? activeTemporalSeries.length >= 2
                     ? `${activeTemporalSeries.length} officiële meetmomenten · ${formatObservationDate(activeTemporalSeries[0].observed_at)} tot ${formatObservationDate(activeTemporalSeries[activeTemporalSeries.length - 1].observed_at)}`
-                    : 'Minstens twee expliciet gedateerde snapshots zijn vereist.'
+                    : 'Voor dit thema is nog geen tweede officieel meetmoment beschikbaar.'
                   : activeThemeDataset
                     ? `${getDatasetSourceDisplayName(activeThemeDataset)} · ${formatObservationDate(activeThemeDataset.observed_at)}`
                     : activeTheme.description}