[r24] Adopt CLI provider and module reliability fixes

[vibeforge1111]

Summary

• adopt safe provider HTTP/network/JSON error handling for spark doctor llm / provider calls
• report missing, unreadable, or malformed module spark.toml manifests as clear CLI errors
• add ok: true to providers-list JSON and use JSON ok for provider/recommend exit codes

Spark Compete source PRs credited

• Inspired by/maintainer-adopted from [spark-compete] Gracefully handle provider API and connection errors in doctor tool #415 and fix: handle HTTPError and URLError in spark doctor llm instead of cra… #309 for provider doctor failure handling
• Inspired by/maintainer-adopted from [spark-compete] fix: load_module crashes on missing or malformed spark.toml #277 for module manifest failure handling
• Focused adoption from [spark-compete] fix: providers recommend/list and recommend llms --json missing ok field and wrong exit code #471 for provider JSON ok / exit-code behavior

Verification

• PYTHONPATH=src python -m pytest tests/test_cli.py -k "load_module or openai_compatible_chat_completion or cmd_providers_list_json or cmd_recommend_llms_json" -q
• PYTHONPATH=src python -m pytest tests/test_cli.py -k "provider or recommend or load_module or spark_toml or openai_compatible_chat_completion" -q