Greptile Summary

This PR adds a Windows-specific fallback to extractGeminiCliCredentials so that Gemini CLI OAuth works even when the gemini binary is absent from PATH. When running on Windows (process.platform === "win32") and APPDATA is set, the function now resolves the package directly from %APPDATA%\npm\node_modules\@google\gemini-cli — the standard location for npm global packages on Windows. The same path is also appended (with deduplication) in resolveGeminiCliDirs for Windows installs where the binary is found in PATH but the package root isn't derivable from the shim location.

Key changes:

• oauth.ts: Restructured early-return logic in extractGeminiCliCredentials into a three-branch if/else if/else, adding the APPDATA fallback as the middle branch; also extended resolveGeminiCliDirs with the same Windows candidate.
• oauth.test.ts: New test overrides process.platform to "win32", sets a fake APPDATA, and confirms the credential extraction succeeds via the APPDATA path.

One minor caveat worth noting: the APPDATA path (%APPDATA%\npm\node_modules) is the default npm global prefix on Windows but is not guaranteed to be correct if the user has customized their npm prefix. This is an acceptable best-effort fallback rather than a complete solution.

Confidence Score: 4/5

• Safe to merge — a targeted, backward-compatible Windows fallback with no risk to Mac/Linux paths.
• The change is well-scoped (two files, one new code path) and is fully guarded by both a process.platform === "win32" check and a truthy APPDATA check, so existing Mac/Linux behavior is completely unchanged. A matching test covers the new branch end-to-end. The one limitation (hardcoded default npm prefix) is inherent to the approach and noted in the PR description; it's a best-effort fallback, not a regression.
• No files require special attention.

_{Last reviewed commit: 8699be4}

Closing to manage active PR count. Will reopen when slot is available.