Adds Level.HEIGHTMAP_VIEWER to AtlasPanel. The viewer loads a body's
terrain_reference heightmap PNG, pairs it with markers.json (roads, rail, POIs,
cities, rivers/oceans/mountains), and renders markers in texture-space via an
AtlasMarkerOverlay Node2D child of a transformed canvas — pan = offset,
zoom = scale.
Pan/zoom is cursor-centred (wheel zooms under the mouse, drag pans), with a
fit-to-view reset on R. Empty markers.json state renders a bare heightmap;
missing terrain_reference shows a themed "terrain data pending (#839)" notice
instead of crashing.
City data sidebar rebuilds from the selected city: name, pop tier, function,
currency zone, Commission presence, shadow zone, gate distance. Pressing N on
a selected city emits economics_link_requested(system_id) — main.gd bridges
this to EconomicsPanel.select_system() + HudGroups.open_app("implant/economics")
as an insert overlay, satisfying the D-191 Phase 2/3 cross-panel integration.
The overlay renders all nine D-191 overlay layers off of per-overlay visibility
flags in AtlasViewer. Overlay toggling for the regional view (#836) plugs into
set_overlay_visible(); the five always-on layers (terrain, infrastructure,
named features, gate markers, political zones) draw by default, the four
toggleable layers draw from placeholder data, and the two locked layers
(stockpile_weeks, production_vs_baseline) remain off until unlocked.
Per D-191 criteria 1, 4, 5.
jpmschweitzer
c33ac8921f
