Expand PostgreSQL benchmark beyond current 10-query slice

[pro-utkarshM]

Goal

Increase benchmark difficulty and size so the selection signal is harder to game and more useful for research.

Scope

Expand beyond the current PostgreSQL authentication slice by adding more chunks, more queries, and harder distractors.

Suggested additions

• add one or more adjacent PostgreSQL sections
• add 10 to 20 more queries
• increase multi-hop and troubleshooting coverage
• add more version-sensitive stale distractors
• enlarge candidate pools where useful

Acceptance criteria

• corpus_chunks_v1.jsonl and queries_v1.jsonl are expanded materially
• candidate pools and context sets are regenerated consistently
• the benchmark still validates cleanly
• analysis output demonstrates whether the larger slice changes the relative strategy rankings