fix: accept readonly arrays in LogTopic type

[nikicat]

Summary

LogTopic is changed from Hex | Hex[] | null to Hex | readonly Hex[] | null. Since readonly T[] is a supertype of T[], this accepts both mutable and readonly arrays.

LogTopicType conditional is updated correspondingly: it now matches readonly Hex[] (which includes Hex[]) and produces readonly primitiveType[].

Motivation

TypeScript's readonly T[] is not assignable to T[]. Users who define topic arrays with as const or receive them from functions returning readonly arrays get type errors when passing them to getLogs, createEventFilter, watchEvent, etc.

Log topic filters are read-only by nature — they're passed to JSON-RPC calls and never mutated — so accepting readonly arrays is both correct and expected.

This is a non-breaking change: all existing mutable-array code continues to work since T[] is assignable to readonly T[].

Related discussions

• How to properly deal with `readonly` values #2671 — readonly values friction with viem APIs
• "The argument of type '0x${string}' is not assignable to the parameter of type 'readonly [0x${string}]'." #1480 — readonly tuple assignability errors with hex values
• request: log `topics` type could be narrowed #163 — log topics type narrowing
• Excessive type inference prevents code reuse, and hurts ecosystem #3549 — excessive type inference hurting ecosystem

Test plan

• All 51 type test files pass (343 tests, no type errors)

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