Add Civ-style hex map visuals and HUD

[YfengJ]

Summary

• replace the civ-lite terrain model with full Civ-style biome tiles, resource overlays, yields, and visibility state
• expand the canvas renderer with clipped hex terrain sprites, resource markers, territory tinting, unit/city banners, health bars, move/attack overlays, and 3-state fog
• add the 4X HUD pieces for resource totals/rates, contextual unit/city panels, event log, minimap territory/viewport overlays, and mobile-friendly layout
• add focused node:test coverage for the terrain model, fog model, empire summary, and HUD markup

Closes #12
Closes #13
Closes #14

Validation

• node --test demo/civ-lite/civ-model.test.mjs
• node --check demo/civ-lite/game.js && node --check demo/civ-lite/sprites.js && node --check demo/civ-lite/civ-model.js
• git diff --check
• Playwright desktop/mobile smoke test on http://127.0.0.1:4187/demo/civ-lite/ with non-empty canvas pixel sample and visible HUD rates

[YfengJ]

CI note: the current Godot Web build failure appears unrelated to this civ-lite change. This PR only changes demo/civ-lite/*, and the same workflow is already failing on upstream main at b86ad79 with Cannot export project with preset "Web" due to configuration errors in make godot-export.

Local validation for the touched civ-lite code passed:

• node --test demo/civ-lite/civ-model.test.mjs
• node --check demo/civ-lite/game.js && node --check demo/civ-lite/sprites.js && node --check demo/civ-lite/civ-model.js
• git diff --check
• Playwright desktop/mobile smoke test with a non-empty canvas sample and visible HUD rates

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud