fix(template): support MiMo audio inputs

[RerankerGuo]

PR type

• Bug Fix
• New Feature
• Document Updates
• More Models or Datasets Support

PR information

MiMo-V2.5 is registered as an audio-capable model, and its official chat
template represents audio with:

<|mimo_audio_start|><|audio_pad|><|mimo_audio_end|>

However, MiMoV2Template.replace_tag() accepted only image and video tags.
Any SWIFT request containing <audio> therefore failed before reaching the
inference backend. In environments without qwen_vl_utils, the audio path
also attempted an unrelated vision import first.

This change:

• renders the official MiMo audio placeholder for vLLM and SGLang;
• leaves the raw audio input unchanged for backend multimodal processing;
• protects <|audio_pad|> when prompt truncation is enabled;
• reports a clear error for Transformers and LMDeploy, which are outside the
  MiMo support scope introduced by support Xiaomi-MiMo-V2.5 inference( sglang / vllm ) #9880;
• keeps existing image and video processing unchanged.

Experiment results

Before:

.venv/bin/python -m unittest tests.general.test_mimo_template
ModuleNotFoundError: No module named 'qwen_vl_utils'
AssertionError: '<|audio_pad|>' not found in [...]
FAILED (failures=1, errors=4)

After:

.venv/bin/python tests/run.py \
  --test_dir tests/general \
  --pattern test_mimo_template.py
SUCCESS (Runs=3, success=3)

.venv/bin/python -m unittest \
  tests.general.test_optional_template_dependencies \
  tests.general.test_model
Ran 2 tests
OK

.venv/bin/pre-commit run --all-files
All hooks passed

[RerankerGuo]

CI note: all three MiMo audio regression tests pass in the CUDA run:

• test_audio_placeholder_for_supported_backends
• test_audio_placeholder_is_protected_from_truncation
• test_audio_rejects_unsupported_backends

The run's only error is the repository-wide
ModuleNotFoundError: transformers.models.gemma3 in
test_gemma3_template.py. The same shared-environment dependency mutation was
traced on #9862:
#9862 (comment).

Lint and the NPU unittest pass.

[RerankerGuo]

@z0o0ey, could you take a look when convenient? This is a focused follow-up
to the MiMo-V2.5 vLLM/SGLang support in #9880.

The change only adds the official MiMo audio placeholder sequence, preserves
raw audio for backend processing, and rejects backends outside #9880's support
scope. Existing image/video paths are unchanged. All three targeted CUDA tests,
lint, and the full NPU suite pass; the unrelated CUDA Gemma3 environment
failure is documented above.