Fix SageAttention naming, enforce auto-precision, and enhance active mode logging

- Renamed `sd2`/`sd3` to `sa2`/`sa3` across CLI, configuration, and internal logic to resolve naming confusion with Stable Diffusion.
- Removed manual `precision` argument from CLI and ComfyUI node to enforce auto-optimization and simplify usage.
- Added explicit logging of the "Active Attention Mode" at the end of the CLI process to confirm which backend was actually used.
- Added "🚀 Executing SageAttention..." console log on first kernel execution to verify optimization activation.
- Updated `FP8CompatibleDiT` to exclude `FlashAttentionVarlen` modules from unnecessary wrapping, fixing a potential performance bottleneck.
- Implemented robust fallback logic for SageAttention (SA3 -> SA2 -> Flash Attention 2 -> SDPA) with version checks.
- Fixed `NameError` crash in `SeedVR2VideoUpscaler` and CLI by removing all residual `precision` variable usage.

src/interfaces/video_upscaler.py

@@ -412,8 +412,7 @@ class SeedVR2VideoUpscaler(io.ComfyNode):
                 dit_offload_device=dit_offload_device,
                 vae_offload_device=vae_offload_device,
                 tensor_offload_device=tensor_offload_device,
-                debug=debug,
-                precision=precision
+                debug=debug
             )
 
             # Prepare runner with model state management and global cache