Phase 1a: Ray, bounds, unproject, Line, frame timing

[robinhilliard]

• EAGL.Math: ray_new/2, ray_intersects_aabb?/2
• EAGL.Math.Bounds: contains_point?/2, intersects?/2, intersects_ray?/2
• EAGL.Camera: unproject/5 (screen to world ray)
• EAGL.Window: render/4 with delta_time, elapsed_time
• EAGL.Line: draw_line/5, draw_lines/4 (GL_LINES)

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Note

Medium Risk
Touches the core EAGL.Window render loop by introducing optional render/4 timing and threading a new start_time through main_loop, which could affect frame scheduling or callback expectations. The rest is additive math/rendering utilities with localized impact.

Overview
Adds picking/collision building blocks: EAGL.Camera.unproject/5 (screen-space to world-space ray), EAGL.Math ray helpers including ray_intersects_aabb?/2, and a new EAGL.Math.Bounds module for point/AABB, AABB/AABB, and ray/AABB intersection checks.

Introduces EAGL.Line for simple GL_LINES rendering (with new line shaders) and extends the window API with an optional render/4 callback that receives %{delta_time, elapsed_time}; the window loop now tracks start_time and prefers render/4 when implemented, falling back to render/3.

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