sdk: fix JSON-RPC batch matching

[0xjc65eth]

Fixes #161

/claim #161
Payment: BTC | bc1qjf2t6dc75c6t2948essyrqec0a08l8zl28fcfh | Bitcoin

Summary:

• Map JSON-RPC batch responses by id and return results in original request order.
• Preserve JSON-RPC item failures as per-item error objects so one failed item does not fail the whole batch.
• Return per-item timeout errors when a batch response omits a request id.
• Add configurable batch fetch timeout and return timeout errors for every request if the batch request is aborted.
• Add focused tests for shuffled response order, partial failure, missing response timeout, and whole-batch timeout.
• Add contributor metadata block at the top of the primary modified file plus CONTRIBUTORS.json record.

Verification:

• npx mocha test/SDKRpcBatchOrdering.test.js -> 4 passing
• npx tsc --noEmit --ignoreConfig --target ES2020 --module commonjs --types node sdk/src/providers/rpc.ts -> clean
• node --check test/SDKRpcBatchOrdering.test.js -> clean
• node -e "JSON.parse(require('fs').readFileSync('CONTRIBUTORS.json','utf8')); console.log('CONTRIBUTORS.json ok')" -> clean
• git diff --check -> clean

Competing PR review:

• Reviewed the competing RPC batch implementation and flagged a missing whole-batch timeout path before submitting this PR.