Retail-anchored design for the missing visual feedback on selection:
four corner triangles + radar-blip colour coding around the selected
entity, drawn via ImGui in screen space.
Retail evidence (named decomp):
* VividTargetIndicator::SetSelected at 0x004f5ce0
* gmRadarUI::GetBlipColor at 0x004d76f0 (Portal / Vendor / Creature /
Player / PK / PKLite / Default colours from pwd._bitfield bits +
IsCreature/IsPlayer/IsPK predicates we already parse)
* VividTargetIndicator::CopyImage at 0x004f5dd0 (tints a source
bitmap by RGBA)
MVP scope:
1. RadarBlipColors helper (Core, with unit tests)
2. TargetIndicatorPanel (App, ImGui draw via background draw list)
3. Wire to existing _selectedGuid from B.4b
4. ~200 LOC + tests
Deferred to follow-ups: off-screen edge arrow, DAT-loaded sprite (MVP
draws procedurally), mesh-tint highlight, player-option toggle, server
selection-relay.
Pairs with #59 (WorldPicker over-pick): the indicator makes the
mis-pick visible, so the user can clear + reselect even before the
underlying picker is tightened.