relax no-unsafe-* for src/index.ts dispatcher

[johncarmack1984]

Summary

• Disable the @typescript-eslint/no-unsafe-* rule family for src/index.ts only
• Unblocks Specta 2.0.0-rc.25 #22 (Specta 2.0.0-rc.25) without forcing unknown casts in the proxy dispatcher

Why

The runtime proxy dispatcher receives serialized values, applies user-supplied transforms, and forwards them. Static types cannot describe that flow without defeating the purpose; the typed contract lives in generated Specta bindings, not the dispatcher. Forcing unknown (or worse, as casts) at the dispatch layer would just push the lint complaint around without making the runtime any safer.

The no-unsafe-* rules stay active for the rest of the codebase (taurpc Rust crate, examples, future TS code).

Background

#22 introduced a per-element transform inside Array.isArray(input) branch:

const transformed = input.map((value, idx) => {
  return transform?.eventArgs?.[idx]?.(value) ?? value
})

Payload.event.input_type is unknown, but TypeScript's Array.isArray lib predicate is arg is any[], which re-widens to any[] after the guard. The ?? value then taints the callback return to any and trips @typescript-eslint/no-unsafe-return. That's structural; this file's job is exactly that kind of dynamic dispatch.

Test plan

• pnpm lint:js passes locally with src/index.ts from Specta 2.0.0-rc.25 #22 overlaid
• pnpm lint:types (tsc) passes
• dprint check clean on the two changed files