feat: add reusable Polygon abstraction

[Donach]

Summary

• add an arbitrary-size Polygon class with builder and vararg construction
• cache and own the polygon boundary rect after sealing
• accelerate exact classification with a 32-world-unit pathing-cell grid: uniform cells answer in O(1), mixed cells inspect only their horizontal-band edge candidates, bounded by O(n)
• expose O(1) vec2 / vec3 to global pathingCell conversion and cell bounds/center
• keep classifyLinear beside the accelerated classify as the exact reference and safe fallback
• store grid data in a reusable 32-array sharded integer arena, avoiding the single JASS-array limit
• provide exact even-odd behavior for convex, concave, degenerate, reversed, and self-intersecting paths
• add overridable debug rendering with optional color, caller-owned handles, and timed automatic cleanup
• retain and deprecate the existing vec2.isInPolygon and vec3.isInPolygon2d APIs for source compatibility

Cell semantics

A cell is INSIDE only when its entire area is inside without touching an edge, OUTSIDE only when disjoint from the polygon, and MIXED when any polygon edge touches or crosses it. classify resolves MIXED cells exactly.

10,000-query evaluation

The accelerated and linear implementations returned identical relations for all 10,000 deterministic points against a 64-edge polygon. The linear path considered 506,048 edges for in-bounds queries; the accelerated path considered 22,486 candidate edges (about 22.5x fewer). 1,978 queries needed edge candidates, so 8,022 were answered without an exact edge scan.

Ownership

Polygon owns its cached bounds and grid allocation. Untimed debug rendering returns a caller-owned ArrayList<lightning>; timed rendering owns and cleans its handles.

Verification

Run inside nix develop /home/daniel/Repositories/tever/tever_main:

• grill typecheck --quiet — passed
• grill test PathingGridTests — 3/3 passed
• grill test ShardedIntStorageTests — 3/3 passed
• grill test PolygonTests — 20/20 passed
• grill test testIsInPolygon — 1/1 passed
• grill test --quiet — passed
• GitHub Actions Build — passed
• git diff --check upstream/master...HEAD — passed

The non-quiet compiler output intentionally reports six deprecation warnings from the restored legacy API test. Warcraft-native lightning creation, coloring, and timed destruction are compile-checked but not Warcraft-runtime verified because Grill cannot execute those natives.

[Frotty]

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[Frotty]

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Codex Review: Didn't find any major issues. Nice work!

Reviewed commit: d9ff9a48ee

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