feat(interior sun): force single shadow cascade option

[davo0411]

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CAUSES LARGE LIGHT LEAKAGE IN CERTAIN INTERIORS LIKE DRAGONSREACH. I have tried everything I can to fix it but the fact that jobArrays is camera based means you look the wrong way and half the culling breaks and lights leak through. This was an issue already, but the forced cascade 1 makes the small bleeds through the walls into full blown light shafts across the interior.

https://cdn.discordapp.com/attachments/1353968487797620856/1434371114880073748/The_Elder_Scrolls_V_Skyrim_Special_Edition_2025.11.02_-_12.37.39.01.mp4?ex=690815b3&is=6906c433&hm=d9706da76437c597357edd85da2d3bcacd9aa3d1f92165c294337d408ce352bc& video showing old light leakage on meshes vs light beam leaks with single cascade.

Adds an optional "ForceSingleShadowCascade" button to Interior Sun Shadows that sets the first cascade for the shadow maps to be the max distance and disables the additional cascades, essentially making the resolution for the interior shadows maximum for the entire distance. This removes previous issues of bleed, light leaking, etc, and also increases the quality of the shadows dramatically with minimal performance degradation. Also makes VL actually visible where it should be, whereas previously the cascades hid this.

Logic behind keeping as toggle is for backward compatibility, some mods may be designed around shadow cascades, or users can opt to disable it for performance.

Increase to minimum shadow distance interior to 3000 units, as 1000 was awful in any room bigger than a shop would cause dramatic visual artifacts, VL bleed/explosions, etc. Fixed description for this, the quality is NOT better with lower distance (due to cascade fix now).

Disabled/Enabled.

Summary by CodeRabbit

Release Notes

• New Features

  • Added "Force Single Shadow Cascade" setting for interior sun optimization to improve shadow quality in interior spaces.

• Improvements

  • Expanded interior shadow distance range (3000–8000 units).
  • Updated shadow setting tooltips with clarified descriptions for better user guidance.