Fix: binary request body corruption in TS→WS→Go transport

[Danny-Dasilva]

Summary

When a binary body is passed via options.body, the TS client calls JSON.stringify({requestId, options}). JSON cannot carry raw bytes: JSON.stringify emits bytes > 0x7F as \uXXXX escapes, Go's decoder stores them as runes, and when Go writes them back to an HTTP request body they re-emit as UTF-8 (e.g. 0xDE → 0xC3 0x9E). The result: upstream servers receive a corrupted payload.

The Go server already has Options.BodyBytes []byte wired as the priority branch (cycletls/index.go:195,347,1418), and encoding/json unmarshals a base64 string directly into []byte. The TS client simply wasn't using it.

This PR:

• Expands the client-side body type to accept Buffer | Uint8Array | ArrayBuffer
• Adds an explicit bodyBytes option
• Auto-routes binary payloads through base64-encoded bodyBytes
• Leaves plain string / URLSearchParams / FormData paths untouched

Reproduction (from the bug report)

const resp = await cycleTLS("https://httpbin.io/post", {
  body: Buffer.from("deadbeefabcdef123456", "hex"),
}, "post");
console.log((await resp.json()).data);

Before: data:application/octet-stream;base64,w57CrcK-w6_Cq8ONw68SNFY= (UTF-8 mangled)
After: data:application/octet-stream;base64,3q2-76vN7xI0Vg== (matches native fetch)

Test plan

• New tests/binary-body-roundtrip.test.ts with 5 cases (local HTTP echo server, byte-for-byte verification):
  • Buffer body with high bytes
  • All 256 byte values round-trip (SHA-256 equality)
  • Uint8Array body auto-routed to bodyBytes
  • Explicit bodyBytes option
  • Plain-string body still flows through body
• Existing tests/urlencoded.test.ts and tests/multipartFormData.test.ts pass unchanged
• Manual verification against https://httpbin.io/post reproduces the original bug and confirms the fix

Notes

• No wire-format change on the Go side — BodyBytes was already there.
• No breaking change: existing string-body callers continue to work.
• If you prefer the "always base64 every body" approach (as suggested in the issue comment), that would be a breaking wire change and can follow as a v3 cleanup.

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