[V1] [Hybrid] Refactor mamba state shape calculation; enable V1 via cli (#20840)

Signed-off-by: Thomas Parnell <tpa@zurich.ibm.com>

vllm/config.py

@@ -1630,6 +1630,9 @@ class CacheConfig:
     checkpoint if available. Otherwise, the scales will default to 1.0."""
     cpu_kvcache_space_bytes: Optional[int] = None
     """(CPU backend only) CPU key-value cache space."""
+    mamba_page_size_padded: Optional[int] = None
+    """ Optional override for mamba page size; used by hybrid mamba/attention
+    models to ensure exact alignment with attention page size."""
 
     # Will be set after profiling.
     num_gpu_blocks: Optional[int] = field(default=None, init=False)
@@ -4882,11 +4885,15 @@ class VllmConfig:
         if architecture is None:
             return
 
-        from vllm.model_executor.models.config import MODELS_CONFIG_MAP
+        from vllm.model_executor.models.config import (
+            MODELS_CONFIG_MAP, HybridAttentionMambaModelConfig)
         cls = MODELS_CONFIG_MAP.get(architecture, None)
         if cls is not None:
             cls.verify_and_update_config(self)
 
+        if self.model_config.is_hybrid:
+            HybridAttentionMambaModelConfig.verify_and_update_config(self)
+
         if self.model_config.task == "classify":
             # Maybe convert ForCausalLM into ForSequenceClassification model.
             from vllm.model_executor.models.adapters import (