fix(embedding): surface upstream errors instead of silent timeout

[ZaynJarvis]

Summary

• Problem: When an embedding provider returns 500 or hangs (e.g., BytePlus endpoint down), ov find shows misleading Network error: HTTP request failed because the Rust CLI times out (60s) before the Python server finishes retrying the embedding call (3+ minutes with SDK retries compounding on top of OV retries). Neither ov health nor ov ready checks embedding connectivity, so users have no way to detect a broken provider.
• Set explicit 30s timeout and disable SDK-level retries (max_retries=0) on the OpenAI embedding client — the server now fails fast enough for the CLI to receive the actual error
• Add try-except in HierarchicalRetriever.retrieve() around embed_compat() with provider/model context in the error message, so users see exactly which backend is broken
• Add embedding connectivity probe to /ready endpoint (10s timeout) — ov ready now catches a broken embedding provider before any search is attempted

Test plan

• All existing embedding unit tests pass (164 passed, pre-existing failures unchanged)
• No new test regressions introduced
• Manual test: start server with a broken embedding config → ov ready should report embedding: error: ...
• Manual test: ov find with broken provider → should return specific error instead of "Network error"

🤖 Generated with Claude Code

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⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🏅 Score: 92

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🔀 Multiple PR themes Sub-PR theme: fix(embedding): surface upstream errors instead of silent timeout Relevant files: openviking/models/embedder/openai_embedders.py openviking/retrieve/hierarchical_retriever.py openviking/server/routers/system.py Sub-PR theme: fix(time): use UTC-aware datetimes consistently Relevant files: openviking/storage/viking_fs.py openviking/utils/time_utils.py

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