test: improve test coverage from 83.78% to 84.10%

Add comprehensive HTTP mocking tests for github.ts and edge case tests for objects.ts:

- Add nock dev dependency (14.0.10) for HTTP mocking infrastructure
- Add 14 tests for github.ts covering fetchGitHub, resolveRefToSha, fetchGhsaDetails, and cacheFetchGhsa
  - HTTP success and error handling (rate limits, 403, 404)
  - Authorization headers and custom headers
  - Tag, annotated tag, branch, and commit SHA resolution
  - GHSA advisory fetching and caching
- Add 7 tests for objects.ts covering internal attributes access and merge edge cases
  - Internal kInternalsSymbol getters (attributes, lazyGetterStats)
  - Merge behavior with null/undefined target/source
  - Array merging skip branches
- Improve objects.ts coverage from 96.12% to 97.67% with 100% function coverage
- Improve github.ts coverage significantly from 19.48%
- Update README badge to reflect new coverage: 84.10%

Author: jdalton

README.md

@@ -2,7 +2,7 @@
 
 [![Socket Badge](https://socket.dev/api/badge/npm/package/@socketsecurity/lib)](https://socket.dev/npm/package/@socketsecurity/lib)
 [![CI](https://github.com/SocketDev/socket-lib/actions/workflows/ci.yml/badge.svg)](https://github.com/SocketDev/socket-lib/actions/workflows/ci.yml)
-![Coverage](https://img.shields.io/badge/coverage-83.78%25-brightgreen)
+![Coverage](https://img.shields.io/badge/coverage-84.10%25-brightgreen)
 
 [![Follow @SocketSecurity](https://img.shields.io/twitter/follow/SocketSecurity?style=social)](https://twitter.com/SocketSecurity)
 [![Follow @socket.dev on Bluesky](https://img.shields.io/badge/Follow-@socket.dev-1DA1F2?style=social&logo=bluesky)](https://bsky.app/profile/socket.dev)

package.json

@@ -742,6 +742,7 @@
     "lint-staged": "15.2.11",
     "magic-string": "0.30.17",
     "make-fetch-happen": "15.0.2",
+    "nock": "14.0.10",
     "normalize-package-data": "8.0.0",
     "npm-package-arg": "13.0.0",
     "pacote": "21.0.1",