Convert module-level optional dependency imports to lazy imports with @dependencies_required

[Copilot]

Multiple modules import optional dependencies (torch, numpy, pandas, datasets, tqdm, rouge, tree_sitter) at module level, causing ImportError when those packages aren't installed.

Changes

• camel/models/reward/skywork_model.py — Add @dependencies_required('torch', 'transformers') on __init__; torch already deferred into methods
• camel/datasets/static_dataset.py — HFDataset via try/except with None fallback + isinstance guard
• camel/datasets/base_generator.py — try/except fallback stub for torch.utils.data.IterableDataset
• camel/benchmarks/ragbench.py — TYPE_CHECKING for Dataset type hints, lazy numpy/datasets in functions, @dependencies_required('datasets') on class init
• camel/benchmarks/nexus.py — @dependencies_required('datasets', 'pandas'), lazy pandas/datasets/tqdm
• camel/benchmarks/apibank.py — Lazy numpy, rouge, tqdm
• camel/benchmarks/apibench.py — Lazy tree_sitter_python, tree_sitter, tqdm
• camel/benchmarks/gaia.py, camel/datagen/evol_instruct/evol_instruct.py, camel/datagen/source2synth/data_processor.py, camel/runtimes/docker_runtime.py — Lazy tqdm
• camel/datagen/self_instruct/filter/filter_function.py — Lazy rouge
• camel/personas/persona_hub.py — Lazy numpy

Pattern

Follows existing codebase convention:

from camel.utils import dependencies_required

class RAGBenchBenchmark(BaseBenchmark):
    @dependencies_required('datasets')
    def __init__(self, ...):
        ...

    def download(self):
        from datasets import load_dataset  # lazy
        self.dataset = load_dataset(...)

All 66 subpackages import cleanly without optional deps installed.

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