Lights: Slice C — Light property panel

[fernandotonon]

Parent epic: #482
Depends on: Slice B

Goal

A dedicated "Light" section in the QML inspector that appears when a light is selected, exposing every editable property with sensible ranges and live preview.

Scope

• New collapsible section in qml/PropertiesPanel.qml: "Light". Visible only when the selection contains lights.
• Bridge through a new LightPropertiesController (src/LightPropertiesController.{h,cpp}, QML_SINGLETON) similar in shape to PropertiesPanelController. Reads/writes through LightManager.
• Properties:
  • Type: directional / point / spot (changing type preserves position/rotation).
  • Enabled toggle.
  • Colour: diffuse + specular as separate pickers (most users will lock them together; provide a "link" toggle, default linked).
  • Intensity: scalar 0–10 with slider + numeric input. Maps to a power scaler on Ogre::Light colour or to setPowerScale where available.
  • Range (point/spot): scalar in scene units.
  • Attenuation: range, constant, linear, quadratic. Provide presets ("Realistic" inverse-square, "Old-school" linear) so users don't need to fiddle with the four numbers directly. Advanced expander shows the raw values.
  • Spot cone (spot only): inner angle, outer angle (in degrees), falloff exponent.
  • Directional softness (directional only, advanced): placeholder for a future PCSS-style param; UI-only no-op for now.
• All slider edits push a single mergeable EditLightPropertyCommand per drag interaction (mirror TranslateCommand::mergeWith).
• Numeric inputs honour Enter to commit; Escape to revert.
• Multi-selected lights show "Mixed" for differing values; editing applies the new value to all.

Acceptance Criteria

• All listed properties are editable and immediately visible in the viewport.
• Spot inner/outer angle clamps correctly (inner ≤ outer ≤ 180°).
• Attenuation presets produce believable point-light falloff curves.
• Slider drags push exactly one undo command, not one per frame.
• Multi-edit applies cleanly and the "Mixed" indicator behaves correctly.
• Sentry breadcrumb scene.light.edit per property class (colour / intensity / range / cone).
• Unit test on LightPropertiesController round-trips every property.

Effort

~5 days.