Raycast python layer (collision raycast foundation)

[sloppynacho]

Summary

Adds the Python layer of the collision-raycast foundation: an ergonomic,
typed Map.Raycast API over the native PyMap bridge, with all geometry math
in Python (the native side is a thin raw bridge — paired C++ change lives on
the Raycastcpp branch of the C++ repo). Enemy/agent detection is intentionally
kept out of the library foundation.

What's included

• Map.Raycast (Py4GWCoreLib/Map.py) — new nested class beside Map.Pathing:
  • Cast(start, end) — combined terrain + walkable-prop (engine returns a point).
  • CastTerrain(start, end) — terrain only (scales the native fraction by seg_len).
  • CastInteractive(start, end) — interactive-prop meshes (doors/gates/gadgets).
  • HasLos(start, end, terrain=, props=) — nearest-block combine; .blocked is the LoS answer.
  • GetProps() / GetPropGeometry(prop_id) — prop enumeration + world-space collision mesh.
  • Returns typed RaycastHit / PropHit / PropInfo; not @frame_cache'd.
• raycast_math.py (Py4GWCoreLib/native_src/internals/) — pure, DLL-free math
  helper (normalize, segment length, blocked decision, hit reconstruction, prop-mesh
  v*M) + the result NamedTuples. Unit-testable without the game running.
• __init__.py — surfaces the native module (import PyMap + rebind).
• stubs/PyMap.pyi — type stub for the thinned raw native signatures.
• Raycaster Tester widget (Widgets/Coding/Debug/Guild Wars/) — renamed from
  LoS Tester; consumes Map.Raycast.*; cone/enemy detection stays widget-side;
  cone rays configurable up to 200.

Design notes

• C++ is a faithful RAW bridge (engine intersect + live-memory walk only); every
  derived calculation lives in Python, so behavior is tunable without a rebuild.
• CastTerrain corrects a pre-existing bug: the bound terrain kernel returns a
  parametric fraction [0,1], not world units — now scaled by seg_len so the
  hit lands at the wall, not the player's feet.
• Availability is explicit: a probe that couldn't run is distinct from "clear LoS"
  (source='unavailable' / n_scanned == -1), so callers never read a failed
  probe as line of sight.

Test plan

• raycast_math unit-tested during development (27 cases) — pass on Python 3.13 (32-bit), no DLL needed.
• All touched modules ast.parse clean.
• In-game parity via the Raycaster Tester widget: terrain/prop/cone behavior matches the pre-refactor LoS Tester; terrain block marker lands on the wall.

Notes

• Breaking native change — requires the matching thinned Py4GW.dll from the C++ Raycastcpp branch. The Python wrapper and the rebuilt DLL must ship together.