fix(auth): trim OAuth credentials during setup

[y4ho0]

Description

Closes #882.

Interactive OAuth setup now trims leading and trailing whitespace from pasted Client IDs and client secrets before validation and persistence. Whitespace-only values are rejected as empty, while characters inside a credential are preserved.

This prevents invisible spaces or newlines copied from Google Cloud Console from producing an invalid_client response during login.

Dry Run Output: Not applicable; this changes interactive credential input and does not create a Discovery API request.

Validation

• cargo fmt --all -- --check
• cargo test --workspace -- --test-threads=1 (785 tests passed)
• cargo clippy -- -D warnings -A clippy::collapsible_match
• cargo clippy -- -D warnings is currently blocked on unchanged main-branch code at helpers/script.rs:173 by the Rust 1.97 collapsible_match lint

Checklist:

• My code follows the AGENTS.md guidelines (no generated google-* crates).
• I have run cargo fmt --all to format the code perfectly.
• I have run cargo clippy -- -D warnings and resolved all warnings. See the documented pre-existing main-branch warning above; the changed code is clean.
• I have added tests that prove my fix is effective or that my feature works.
• I have provided a Changeset file to document my changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: cb7c6a9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@googleworkspace/cli	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.