ci: speed up Windows node checks

[kmbroai]

Summary

• Split each Windows Node lane into seven isolated Bun shards plus a package-verification job, while retaining the original windows-latest / node-22 and windows-latest / node-24 aggregate check names.
• Preserve every Windows test: the runner discovers every tests-ts/*.test.ts file, asserts complete assignment, and uses complementary filters only to divide the oversized api.test.ts file.
• Move typecheck and formatting onto the lightest Windows shard so package smoke is no longer serialized behind unrelated static checks.
• Replace the slow Windows pnpm action/cache path with an exact pnpm@11.9.0 install and avoid caches unused by test shards.
• Reuse already-parsed npm tarball bytes for package payload checks instead of spawning tar -xOf per asset; keep both tar listings, archive validation, installed-package smoke, CLI smoke, and nested-worker smoke.

Timing

Baseline main run 31219820557:

• Windows Node 22: 512s total, 349s Test, 59s Inspect package
• Windows Node 24: 439s total, 315s Test, 43s Inspect package
• Ubuntu Node 22: 109s total
• Ubuntu Node 24: 117s total

Final PR run 31224054986:

• Windows Node 22 critical path: 108s; slowest shard 106s
• Windows Node 24 critical path: 112s; slowest shard 112s
• Ubuntu Node 22: 128s
• Ubuntu Node 24: 114s

Coverage

Final run 31224054986 on both Windows Node versions:

• 934 pass, 53 platform skips, 0 fail
• 987 tests across 41 files
• Typecheck, formatting, build, pack, package inspection, installed-package smoke, CLI smoke, and nested-worker smoke all pass

Test plan

• pnpm --dir sdk/typescript run types
• pnpm --dir sdk/typescript run format
• Default full suite under the sandbox ownership normalizer: 979 pass, 10 skip, 0 fail; 989 tests across 41 files in 77.47s
• Windows shard runner under the same normalizer: 979 pass, 10 skip, 0 fail; 989 tests across 41 files in 41.20s
• pnpm --dir sdk/typescript run build
• pnpm --dir sdk/typescript pack --pack-destination /tmp/codex-security-dist
• node sdk/typescript/scripts/check-package.mjs /tmp/codex-security-dist/openai-codex-security-0.1.7.tgz
• GitHub Actions run 31224054986