Fix auto-update bun install cwd - #254

Greptile Summary

This PR fixes bun install running in the active project directory (ctx.directory) during auto-update, which polluted pnpm project roots with bun.lock and node_modules. The fix redirects the install to CACHE_DIR (the OpenCode cache directory) via a new exported getAutoUpdateInstallDir() helper, and adds a regression test that pins the directory to the cache path using Bun's module mocking.

Confidence Score: 5/5

Safe to merge — the fix is correct and well-targeted; the only finding is a minor unused parameter cleanup.

All remaining findings are P2 (unused ctx parameter in runBunInstallSafe after the refactor). The core bug fix is correct: using CACHE_DIR as the bun install cwd prevents polluting project roots. The regression test is properly structured using Bun module mocking. No P0/P1 issues found.

No files require special attention.

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant Hook as createAutoUpdateCheckerHook
    participant BGCheck as runBackgroundUpdateCheck
    participant BunInstall as runBunInstallSafe
    participant CacheDir as CACHE_DIR (~/.cache/opencode)

    Hook->>BGCheck: runBackgroundUpdateCheck(ctx, autoUpdate)
    BGCheck->>BGCheck: invalidatePackage(PACKAGE_NAME)
    BGCheck->>BunInstall: runBunInstallSafe(ctx)
    BunInstall->>BunInstall: installDir = getAutoUpdateInstallDir()
    Note over BunInstall: Previously: cwd = ctx.directory (project root)<br/>Now: cwd = CACHE_DIR
    BunInstall->>CacheDir: Bun.spawn(['bun', 'install'], { cwd: installDir })
    CacheDir-->>BunInstall: exit code
    BunInstall-->>BGCheck: success / failure
    BGCheck-->>Hook: showToast(result)

_{Reviews (1): Last reviewed commit: "Fix auto-update bun install cwd" | Re-trigger Greptile}