feat(search): add RERANK parameter for HNSW vector fields

[nkaradzhov]

This pull request adds support for the RERANK parameter on HNSW vector field definitions in FT.CREATE, introduced in Redis 8.10 (RediSearch, for disk-based vector indexes).

• New optional RERANK?: boolean on the HNSW schema vector field type.
• When set, the client emits RERANK TRUE or RERANK FALSE as a key-value pair in the field definition.
• No default value — the parameter is only sent when explicitly provided, matching the server contract where users must specify it for disk-based indexes.

The parameter is HNSW-only; FLAT and SVS-VAMANA are unaffected and the type narrowing makes RERANK a compile error on those algorithms. The value is passed through as-is, so MVP (TRUE-only) vs later (FALSE allowed) validation stays server-side.

Note: creating a disk-based vector index is a server capability and is not exposed as an FT.CREATE client flag, so the 8.10-gated live test asserts the parameter reaches the server and is recognized (rejected only for the index type, not as a syntax error).

🤖 Generated with Claude Code

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Note

Low Risk
Opt-in schema serialization in the search client only; no changes to connection, auth, or existing index defaults.

Overview
Adds optional RERANK on HNSW vector fields in FT.CREATE (Redis 8.10 / disk-based indexes). When set, the client emits RERANK TRUE or RERANK FALSE; if omitted, nothing is sent.

Types limit RERANK to HNSW so FLAT and SVS-VAMANA schemas are unchanged. Tests cover argument transformation and a version-gated integration check that the server accepts the token (OSS tests expect a disk-based index rejection, not a syntax error).

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