feat(asr): add optional SenseVoice/FunASR provider

[LauraGPT]

Summary

• add a local SenseVoiceASR provider backed by FunASR, with lazy model loading, model caching, serialized inference, 20-minute chunking, native timestamp parsing, and a separately configured fsmn-vad model
• expose model and device selection through the CLI, TOML configuration, environment variables, and desktop settings
• normalize encoded audio bytes to 16 kHz mono WAV before inference
• keep funasr, torch, and torchaudio in the optional sensevoice extra and hide SenseVoice from the desktop model list when that complete runtime is unavailable
• add focused provider, dependency-gating, and CLI configuration tests

The default iic/SenseVoiceSmall checkpoint supports Chinese, Cantonese, English, Japanese, and Korean. This PR does not add the OpenAI-compatible FunASR server, Paraformer, speaker diarization, or a universal performance claim across FunASR checkpoints.

Desktop release builds do not currently bundle the optional PyTorch/FunASR runtime. With this PR, those builds no longer advertise an unusable SenseVoice option; source/Python installations can enable it with pip install 'videocaptioner[sensevoice]'.

Validation

• TDD regression: dependency-incomplete desktop model-list test failed before the runtime gate, then passed after the fix
• uv run --frozen pytest tests/test_cli tests/test_dubbing tests/test_asr/test_sensevoice_asr.py tests/test_asr/test_platform_utils.py -q (92 passed)
• uv run --frozen ruff check and ruff format --check on all changed files
• uv run --frozen pyright videocaptioner/core/utils/platform_utils.py (0 errors)
• uv sync --frozen --extra sensevoice followed by successful imports of FunASR 1.3.14, Torch 2.13.0, and torchaudio 2.11.0
• real CPU transcription of the repository's Chinese and English MP3 fixtures (10 timestamped segments each, non-empty expected text)
• uv build (sdist and wheel built successfully)
• git diff --check

Full-repository pyright still reports four pre-existing return-type errors in translation/TTS modules that are outside this PR's diff.

Closes #1137

[LauraGPT]

Follow-up for head 658b2ee: the three new workflow runs are still action_required with zero jobs, so no test has failed; they need maintainer approval before GitHub can start them:

• CI
• Claude Code Review
• Build Desktop Apps

This head also fixes a desktop packaging gap found during review: SenseVoice is now hidden unless the complete optional runtime (funasr, torch, and torchaudio) is available. Local verification is green: 92 focused tests, Ruff and targeted Pyright, sdist/wheel build, optional-runtime imports, and real CPU transcription of the Chinese and English fixtures.

Could a maintainer approve the current runs when convenient?

[LauraGPT]

Pushed head aeaa7de5e6cafab6655b0210920b64c6027a6f7f after rechecking this PR in an environment that installs the optional SenseVoice runtime.

What changed:

• Fixed the missing-optional-dependency test so it patches the same import path used by production code: importlib.import_module("funasr"). This keeps the test meaningful even when videocaptioner[sensevoice] is installed.
• Ran the current project Ruff formatter on the PR-touched CLI/config/entity files so the current locked toolchain passes ruff format --check.

Fresh validation on ind-gpu8 with uv sync --group dev --extra sensevoice:

uv run pytest tests/test_asr/test_sensevoice_asr.py tests/test_asr/test_platform_utils.py tests/test_cli/test_config.py tests/test_cli/test_parser.py -q
# 78 passed

uv run ruff check <PR-touched ASR/CLI/test files>
uv run ruff format --check <PR-touched ASR/CLI/test files>
uv run pyright videocaptioner/core/asr/sensevoice.py videocaptioner/cli/validators.py
python -m py_compile <PR-touched Python files>
git diff --check
uv build --sdist --wheel

All of the above passed. GitHub reports the PR as mergeable; the remaining workflow runs still need maintainer approval before they can execute on the fork.