fix: default Google Drive OAuth to My Drive

[CruxExperts]

Summary

• Pass rclone's config_change_team_drive=false default through every non-interactive config create/update continuation.
• Keep bbman auth-gdrive focused on normal My Drive remotes; shared-drive selection remains explicit and unsupported by this helper.
• Add regression coverage and align the README, Quickstart, and management guide.

Verification

• uv run pytest: 620 passed
• Ruff, py_compile, version sync, publishing readiness, generated CLI metadata, and git diff --check passed
• Independent review: no findings
• No credentials or tokens committed

Fixes the post-merge review finding on PR #16.