Raise real exceptions instead of strings in the runtime Python bindings

[LeonardNJU]

Fixes #3523.

raise "some message" is invalid in Python 3 — a str is not an exception. The
interpreter discards the intended message and raises

TypeError: exceptions must derive from BaseException

instead. Paired with the surrounding bare except:, the original cause is lost as well,
so the user is told to install a package they may already have while the real failure is
invisible.

What this looked like in practice

funasr was installed. The import failed on a missing transitive dependency:

File ".../funasr/utils/load_utils.py", line 9, in <module>
    import torchaudio
ModuleNotFoundError: No module named 'torchaudio'

What I saw:

File ".../funasr_onnx/sensevoice_bin.py", line 66, in __init__
    raise "You are exporting onnx, please install funasr and try it again..."
TypeError: exceptions must derive from BaseException

The message pointed at the wrong package, and the traceback pointed at the wrong error.
Diagnosing it meant reading the library source and reproducing the import by hand. I hit
the same wall a second time on onnxscript (required by newer torch.onnx), and a third
time when loading from a local path — the model_dir branch fires on any failure, so a
mistyped path also surfaced as TypeError.

The change

All 30 occurrences under runtime/python (7 files, both funasr_onnx and
funasr_torch):

# before
try:
    from funasr import AutoModel
except:
    raise "You are exporting onnx, please install funasr and try it again. ..."

# after
try:
    from funasr import AutoModel
except ImportError as e:
    raise ImportError(
        "You are exporting onnx, please install funasr and try it again. ..."
    ) from e

• guarded imports → except ImportError as e: / raise ImportError(...) from e
• everything else → except Exception as e: / raise RuntimeError(...) from e

from e preserves the original traceback, which is the point — a missing torchaudio
now stays visible under the friendly message. Narrowing the bare except: also stops
unrelated failures from being reported as a missing package.

Messages are unchanged. The only behavioural difference is the exception type, which
previously could not be caught by anything anyway.

Verification

• raise " no longer appears anywhere under runtime/python
• every changed file passes python -m py_compile
• chaining behaves as intended:

外层信息: please install funasr: pip3 install -U funasr
真实原因: No module named 'nonexistent_module_xyz'

I deliberately did not run black over these files. It reformats unrelated code in
them (the tree is not currently black-clean), which would have buried a 140-line fix in a
280-line diff. The new code follows the project's 100-column style by hand. Happy to run
the formatter if you would rather have it.

Two occurrences outside runtime/python are left alone as out of scope:
funasr/models/qwen3_asr/model.py and funasr/download/runtime_sdk_download_tool.py.

Context: found while building a local-ASR adapter for Jitsi Meet
(https://github.com/LeonardNJU/jitsi-local-asr) that runs SenseVoice and streaming
Paraformer via funasr_onnx on an ARM box.