build: prepare tsconfig and relay types for TypeScript 6 (#2348)

src/upstreamproxy/relay.ts

@@ -63,7 +63,7 @@ const PING_INTERVAL_MS = 30_000
  * protobufjs would be the general answer; for a single-field bytes message
  * the hand encoding is 10 lines and avoids a runtime dep in the hot path.
  */
-export function encodeChunk(data: Uint8Array): Uint8Array {
+export function encodeChunk(data: Uint8Array): Uint8Array<ArrayBuffer> {
   const len = data.length
   // varint encoding of length — most chunks fit in 1–3 length bytes
   const varint: number[] = []

tsconfig.json

@@ -16,7 +16,7 @@
     "declaration": false,
     "outDir": "./dist",
     "rootDir": "./src",
-    "baseUrl": ".",
+    "types": ["bun", "node"],
     "paths": {
       "src/*": ["./src/*"]
     }