docs: clarify spotlight cone angles are half-angles

[willeastcott]

Summary

• Clarifies in the LightComponent.innerConeAngle / LightComponent.outerConeAngle JSDoc that these are half-angles (measured from the light's direction axis to the cone edge), and calls out the resulting full beam angle.
• No runtime behavior change — documentation only.

Motivation

The current wording ("the angle at which the spotlight cone has faded to nothing") reads naturally as the full beam angle. That's the convention every major DCC / engine uses — Unity, Maya, 3ds Max, Unreal, Blender all treat a "45° spot" as a 45° cone. PlayCanvas actually stores the half-angle (which is the natural form for the shader math and matches glTF KHR_lights_punctual), so a user setting outerConeAngle = 45 gets a 90° cone, not a 45° one. The default 45 compounds the confusion.

This PR doesn't change the convention (behavior stability + glTF alignment make that a separate discussion) — it just stops the docs from quietly misleading readers.

Before / After

Before:

/**
 * Sets the angle at which the spotlight cone has faded to nothing. The angle is specified in
 * degrees. Affects spot lights only. Defaults to 45.
 *
 * @type {number}
 */
set outerConeAngle(arg) { ... }

After:

/**
 * Sets the half-angle (measured in degrees from the light's direction axis to the cone edge)
 * at which the spotlight cone has faded to nothing. The full outer beam angle is twice this
 * value. Affects spot lights only. Defaults to 45 (i.e. a 90 degree full outer beam).
 *
 * @type {number}
 */
set outerConeAngle(arg) { ... }

innerConeAngle gets the equivalent treatment (half-angle, full inner beam callout, default 40 → 80° full inner beam).

Test plan

• npm run lint clean
• Docs-only change; no runtime tests needed.

[Copilot]

Pull request overview

Clarifies the LightComponent spotlight cone angle documentation to explicitly state that innerConeAngle / outerConeAngle are half-angles, and explains the implied full beam angle to reduce user confusion without changing runtime behavior.

Changes:

• Update innerConeAngle setter/getter JSDoc to describe half-angle semantics and the derived full inner beam angle.
• Update outerConeAngle setter/getter JSDoc to describe half-angle semantics and the derived full outer beam angle.

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