rules_bun

Bazel rules for bun.

Current status

Phase 1 bootstrap is in place:

• Bun toolchain rule and provider (/bun/toolchain.bzl)
• Platform-specific Bun repository downloads (/bun/repositories.bzl)
• Toolchain declarations and registration targets (/bun/BUILD.bazel)
• Smoke test for bun --version (//tests/toolchain_test:bun_version_test)