fix(rueidiscompat): reject unsupported slice fields

[fallintoplace]

What

• Return an error for unsupported slice fields in Scan.

Why

• A field like []int keeps its old value while Scan returns success.

Implementation

• Use the existing unsupported-type error.
• Add cases for slice types, pointers, byte slices, and custom scanners.

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Note

Medium Risk
Changes Scan from silent no-op to error for many slice field types, which may surface latent misuse but fixes incorrect success semantics.

Overview
Scan no longer reports success for slice fields it cannot decode. Only []byte / []uint8 still get the Redis string as raw bytes; other slice kinds (e.g. []int, []string, nested slices, named slice types, *[]int) now return redis.Scan(unsupported …) and leave the destination field unchanged.

Tests cover unsupported-slice errors and value preservation, byte-slice and pointer cases, and custom slice types that implement ScanRedis or UnmarshalText.

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[rueian]

Hi @fallintoplace, why do you need this? This doesn't seem to align with go-redis.

[fallintoplace]

I think you are right, I will close this.