[Fix] Refines decode mode padding condition for uniform queries (#5164)

### What this PR does / why we need it?
The reason why we cannot use `self.cudagraph_batch_sizes[-1]` is that
it's actually not the max number of tokens to be padded in
`FULL_DECODE_ONLY` mode, much larger instead. And it's trimmed only
before capturing to `compilation_cases`, this really caused us lots of
trouble.

Updates the logic to ensure padding occurs only when the number of input
tokens falls within a valid uniform decode query range, improving
consistency and avoiding unnecessary padding in specific decode modes.

### Does this PR introduce _any_ user-facing change?
None.

### How was this patch tested?
None.
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>

vllm_ascend/worker/model_runner_v1.py

@@ -1008,8 +1008,9 @@ class NPUModelRunner(GPUModelRunner):
 
             # TODO: We should make this official ASAP. Also note that if we pad here,
             # the builders won’t need to add any extra padding.
+            max_decode_tokens = self.scheduler_config.max_num_seqs * self.uniform_decode_query_len
             if self.compilation_config.cudagraph_mode.decode_mode() == CUDAGraphMode.FULL and \
-                uniform_decode and num_input_tokens <= self.cudagraph_batch_sizes[-1]:
+                uniform_decode and self.uniform_decode_query_len <= num_input_tokens <= max_decode_tokens:
                 num_reqs_padded = num_input_tokens // self.uniform_decode_query_len
                 pad_size = num_reqs_padded - num_reqs
                 if pad_size > 0: