FIX: n_kv_tiles as Python int (s_k//128) for range() unrolling

cute.size() returns a CuTeDSL symbol, not a Python int.
range() on a symbol can't iterate — the loop never unrolls.
Now n_kv_tiles is computed in __init__ as s_k // 128 (Python int).

tests/unit/test_fmha_v3_stage_c_full.py

@@ -38,6 +38,7 @@ class FmhaV3StageC:
     def __init__(self, s_k=128, scale_softmax=None):
         # s_k MUST equal actual sequence length n (compile-time constant for V layout).
         self.s_k = s_k
+        self.n_kv_tiles = s_k // 128  # Python int — needed for range() unrolling
         self.acc_dtype = Float32; self.qk_acc_dtype = Float32
         self.q_dtype = BFloat16; self.o_dtype = BFloat16; self.c_dtype = BFloat16
         self.use_2cta_instrs = False; self.epilog_sync_bar_id = 1
@@ -207,7 +208,7 @@ class FmhaV3StageC:
             # Python range() unrolls at trace time. Each iteration emits a
             # separate cute.copy with a distinct compile-time Int32 constant.
             # We proved Int32(1) hardcoded works — by induction Int32(k) works.
-            for kt in range(n_kv_tiles):
+            for kt in range(self.n_kv_tiles):
                 coord = Int32(kt)
                 kvh = kvp.acquire_and_advance(pk)
                 cute.copy(tma_k, tBgK[(None, coord)], tBsK[(None, kvh.index)], tma_bar_ptr=kvh.barrier)
@@ -224,7 +225,7 @@ class FmhaV3StageC:
             kvc.reset(); pk = kvc.try_wait()
             acc_st = pipeline.make_pipeline_state(pipeline.PipelineUserType.Producer, self.num_acc_stage)
             acc_pipe.producer_acquire(acc_st)
-            for kt in range(n_kv_tiles):
+            for kt in range(self.n_kv_tiles):
                 kvh = kvc.wait_and_advance(pk); pk = cutlass.Boolean(1)
                 sh = s_prod.acquire_and_advance()
                 qk_mma.set(tcgen05.Field.ACCUMULATE, False)
@@ -302,7 +303,7 @@ class FmhaV3StageC:
             row_sum = Float32(0.0)
             scale_log2 = Float32(self.scale_softmax_log2)
 
-            for kt in range(n_kv_tiles):
+            for kt in range(self.n_kv_tiles):
                 si_handle = s_cons.wait_and_advance()
 
                 # Load S[kt]