Add scan_factor and max_candidates support for Pinecone dedicated rea…

[dmsmith25]

…d nodes

• Add --pinecone_scan_factor and --pinecone_max_candidates CLI args, passed through to index.query() for dedicated read node indexes
• Validate dedicated read node requirement via REST API (2025-10 version) rather than a CLI flag check, since describe_index SDK response omits read_capacity info
• Auto-detect namespace when index has exactly one namespace
• Auto-detect synthetic workload dimensions from existing Pinecone index when --synthetic_dimensions is not explicitly specified

Problem

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Solution

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Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

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