fix(typegen): type TRANSFORM_MAP callbacks against actual method types

[johncarmack1984]

Summary

The TRANSFORM_MAP generator emits per-method transform callbacks like (v) => v.map((i) => i). Without parameter annotation, those v/i/response identifiers trip noImplicitAny in strict-mode consumers, and consumers have no clean place to silence it (the whole file is auto-generated).

Approach

Keep the outer parameter unknown so the callback remains contravariantly assignable to the runtime's TransformFn = (value: unknown) => unknown. Narrow once inside the body via const t = v as <method-type>. The runtime expression already references that bound identifier, so the typed binding satisfies strict mode without weakening the runtime contract.

Before:

export const TRANSFORM_MAP = {
  airports: {
    get_airport_bounds: {
      args: [null],
      eventArgs: [null],
      result: (v) => v == null ? v : v.map((i) => i),
    },
  },
};

After:

export const TRANSFORM_MAP = {
  airports: {
    get_airport_bounds: {
      args: [null],
      eventArgs: [null],
      result: (v: unknown) => {
        const t = v as [number | null, number | null, number | null, number | null] | null;
        return t == null ? t : t.map((i) => i);
      },
    },
  },
};

The type for t is rendered from the same DataType the generator already had on hand (Deserialize-phase for args, Serialize-phase for event args and results -- matching what the IPC bridge actually passes through the callback). Channel handlers get the same treatment with the inner response parameter typed against the channel's payload DataType.

Test plan

• cargo build -p taurpc clean
• Regenerated bindings on a downstream consumer (fltsci); the prior 10 TS7006: Parameter 'v' implicitly has an 'any' type errors clear without any consumer-side @ts-ignore or tsconfig escape hatches
• No runtime change -- only the emitted TypeScript shape changes
• Draft for now -- pin gets validated end-to-end via the fltsci specta rc.25 bump branch before un-drafting

Notes

The runtime types (TransformFn, MethodTransform, TransformMap in src/index.ts) intentionally stay at (value: unknown) => unknown -- generators and hand-written consumers should both be allowed to widen to that shape.