[Perf][Cosmos3] Add SeaCache support for Cosmos3 (#6922)

Signed-off-by: Yuliya Zhautouskaya <yzhautouskay@nvidia.com>

vllm_omni/diffusion/data.py

@@ -541,6 +541,8 @@ class DiffusionCacheConfig:
                     scm_steps_mask_policy, scm_steps_policy
         - MagCache: mag_threshold, mag_max_skip_steps, mag_retention_ratio,
                     mag_ratios, mag_calibrate
+        - SeaCache: sea_threshold, sea_residual_order,
+                    sea_max_consecutive_cached, sea_power_exp
         - step_cache: step_cache_dit_enabled, velocity_sim_thresholds,
                           velocity_skip_countdowns, step_cache_dit_min_history
 
@@ -560,6 +562,12 @@ class DiffusionCacheConfig:
     rel_l1_thresh: float | None = None
     coefficients: list[float] | None = None  # Uses model-specific defaults if None
 
+    # SeaCache parameters [sea_cache only]
+    sea_threshold: float = 0.25
+    sea_residual_order: int = 1
+    sea_max_consecutive_cached: int = 2
+    sea_power_exp: float = 3.0
+
     # MagCache parameters [mag_cache only]
     # Default: 0.24 threshold for accumulated magnitude error
     mag_threshold: float = 0.24