Fix Footprints RT shader compilation regressions

[JaimeCamachoDev]

Summary

• rewrite the Footprints stamp and fade blit passes to use UnityCG helpers so they compile without TEXTURE2D_X
• drop the fog dependency from the instanced decal shader to avoid the missing include on URP
• normalize the demo walker's forward vector before LookRotation to silence the normalization assertion in play mode

Testing

• not run (Unity play mode required)

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https://chatgpt.com/codex/tasks/task_b_6909d5418f408326a9074dae523f4bbb