Restore GeoLibre download route and reuse LULC rasters

[amit-spatial]

What changed

• restore the GeoLibre-based LandscapeExplorer at /download_layers
• add a route contract test that rejects the legacy map/sidebar implementation
• remove the empty Climate group from the GeoLibre layer panel
• point all Level 1, Level 2, and Level 3 LULC entries at the same Level 3 coverage for each year
• render that shared coverage with the corresponding Level 1, Level 2, or Level 3 GeoServer style
• stop visibility-only viewer snapshots from reloading the full GeoLibre project
• preserve native raster sources when a loaded LULC layer is toggled off and on
• update the KYL legend directly from GeoLibre state snapshots, without reloading the iframe project
• display the initial legend expanded over the map and automatically reopen/select the palette for each newly visible LULC style
• retain the Level 3 WCS coverage for GeoTIFF downloads and document the shared-source contract

Why

An earlier revert kept /download_layers mapped to LandscapeExplorer but replaced that page orchestration with the older OpenLayers map and Filters & Data sidebar. This restores the GeoLibre page that existed immediately before that revert.

The three LULC levels contain identical raster data and differ only in styling. The integration previously reused the Level 3 coverage, but each visibility snapshot was echoed back as a complete project load. That recreated native raster sources and caused already-loaded WMS tiles to be requested again. Simply stopping that reload also stopped the iframe legend plugin from receiving visibility changes, so the legend now follows the same snapshots independently.

The first overlay implementation remained collapsed and sat below GeoLibre’s right-hand style panel. It is now expanded initially, positioned over the map, and reopened whenever a new visible legend is detected.

Impact

/download_layers once again loads the hosted GeoLibre workspace. Users keep the existing per-year Level 1, Level 2, and Level 3 choices, all backed by the canonical Level 3 coverage. Toggling an existing layer off and on no longer replaces the project or recreates its raster source. Each newly displayed LULC level visibly opens its own prepared class palette. A first view of a different level can still request its distinct server-rendered WMS style tiles; it does not load a separate Level 1 or Level 2 raster dataset.

Validation

• 4 focused suites passed, 20 tests total
• legend regression confirms the initial palette is expanded and a newly visible Level 2 style reopens/selects the Level 2 palette
• shared-source regression confirms visibility-only raster changes do not send another load-project
• route regression confirms /download_layers points to the GeoLibre page and excludes legacy Map/RightSidebar imports
• focused ESLint and git diff --check passed
• production build completed successfully; existing unrelated ESLint warnings remain
• npm start compiled successfully and /download_layers returned HTTP 200
• headless Chrome loaded the hosted GeoLibre 2.5.0 iframe and visually confirmed the initial legend over the map
• live iframe toggles confirmed 2017–18 Level 2 shows Trees and forests/Crops and Level 1 shows its five prepared classes
• live Level 3 WMS returned valid PNG tiles for all three named LULC styles