Bun switched its default lockfile from the binary bun.lockb to the
text-based bun.lock, but detectFromLockFile() only ever checked for
bun.lockb — a project using modern Bun would never be detected as
using Bun at all.
Added bun.lock as the primary lockfile with bun.lockb kept as a
recognized legacy alias, so either format is detected correctly.
Also ignore stray bun.lock/bun.lockb at the repo root: yarn is this
repo's canonical package manager (package.json "packageManager"), so
a lockfile from someone running `bun install` locally shouldn't get
picked up by git status.
