feat: civ-style hex map with Kenney HD tiles

[keanji-x]

Summary

• Replace procedural cartoon textures with Kenney Hexagon Pack 4x tiles (480×561 px, CC0 licensed)
• Rewrite hex rendering: pointy-top grid, Civ-style culture borders (glowing lines at territory edges), territory color overlays (28% tint unifying same-owner hexes)
• Per-owner roof recoloring: pixel-level green→owner-color swap on building tiles, preserving lighting
• Add click-to-expand Portal modals for Memories, Inbox, Chronicle, Combat Log, and World Events panels
• Territory hex list capped with scrollable overflow to prevent panel squeezing

Changes

Area	Files	What changed
Assets	public/tiles/kenney/ (161 PNGs)	Kenney 4x hex tiles — terrain, buildings, military, etc.
Hex grid	HexGrid.ts	Pointy-top, 480×561 base, 0.25x display scale, hex vertices
Terrain	TerrainGen.ts	5 clean biomes (grass/sand/dirt/stone/mars) mapped to Kenney tiles
Map scene	HexMapScene.ts	Load individual PNGs, territory overlays, culture border algorithm
Buildings	LocationCluster.ts	Kenney building tiles + roof recolor per owner
Agents	AgentSprite.ts	Colored circle markers replacing meeples
Layout	WorldLayout.ts	Adapted to new hex dimensions
Roof recolor	utils/recolorRoof.ts	Canvas pixel manipulation for green→owner color
UI modals	EntryModal.tsx	React Portal full-screen expand for entry lists
UI panels	AgentDetail.tsx, LocationDetail.tsx, Sidebar.tsx	Click-to-expand on all entry panels

Test plan

• Verify hex map renders with Kenney terrain tiles on Gravity testnet
• Check territory color overlays and culture border lines between different owners
• Confirm building roof colors differ per owner (red, blue, green, gold, etc.)
• Click Memories/Inbox/Chronicle/Combat Log/World Events → modal opens centered, scrollable
• Close modal via X button or clicking backdrop
• Territory hex list scrolls within its card without squeezing other panels

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