The plugin builds with `bun build --target bun` and runs under OpenCode
CLI (Bun SEA) but also under OpenCode Desktop (Electron / Node V8) where
`globalThis.Bun` does not exist. Mirror the existing `bun-spawn-shim.ts`
pattern for three more Bun runtime APIs:
- bun-file-shim: bunFile()/bunWrite() backed by node:fs/promises with
ArrayBuffer slicing to avoid Node Buffer pool exposure
- bun-hash-shim: pure-JS XXH32, bit-exact with Bun.hash.xxHash32 verified
by 1200-pair fuzz comparison so existing hashline LINE#ID tags remain
stable across runtimes
- bun-which-shim: synchronous PATH walker with Windows .exe/.cmd/.bat/.com
extensions plus isUnsafeCommandName guard that rejects path separators,
parent traversal, drive letters and null bytes before any probe
Each shim uses the canonical `runtime.Bun !== undefined` detection and
delegates to native Bun under IS_BUN, otherwise uses Node primitives.
Each ships with a co-located test that exercises both branches via the
`node:vm.runInNewContext` pattern from bun-hash-shim.test.ts.
YeonGyu-Kim