fix: filter Neptune query params

[cnYui]

Summary

• Filter Neptune execute_query() kwargs down to non-None parameters actually referenced by the Cypher query after flattening nested params.
• Keep referenced params such as LIMIT $limit, while dropping live-path extras like search_vector, min_score, database_, and routing_ before they reach Neptune openCypher.
• Alias fallback community AOSS writes from communities to the Neptune community_name index.
• Add focused NeptuneDriver regression coverage for both follow-up paths.

Context

This is a small follow-up for the live Neptune/AOSS path findings discussed in #1529 and #1539. It intentionally does not include the other #1539 fixes (clone() handling or AOSS bulk action _id changes), so it can stay focused on query parameter filtering and community index naming.

Testing

• uv run --frozen --extra dev --extra neptune pytest tests/driver/test_neptune_driver.py -q
• uv run --frozen --extra dev --extra neptune ruff check graphiti_core/driver/neptune_driver.py tests/driver/test_neptune_driver.py
• uv run --frozen --extra dev --extra neptune ruff format --check graphiti_core/driver/neptune_driver.py tests/driver/test_neptune_driver.py
• uv run --frozen --extra dev --extra neptune pyright graphiti_core/driver/neptune_driver.py

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[cnYui]

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