[davidcollom]

3Drop keeps saved models behind an interactive Google login, and its cloud-browser session cannot be exported into a NAS process. This adds a Go backup service that can consume a complete browser-generated JSON inventory through Google Drive, archive likes and collection references, and download supported model files locally.

• Cobra/Viper CLI: cookie sync, saved-response import, local handoff, drive publish, drive sync, and provider/explicit-link downloads. Flags override environment and config.
• Strict complete-inventory contract with counts, model IDs, source URLs, titles and collection IDs/membership. Partial, inconsistent, stale and older inventories cannot replace the catalogue. Prior files and snapshots survive removals.
• Drive file creation/update and authenticated reads by stable file ID, with renewable authorised-user OAuth credentials in private mounted files. No 3Drop/Google sign-in tokens or expiring model download links belong in the inventory.
• DOM-only browser helper and operator runbook; provider interface with Printables as the first adapter. Concurrent transfers honour --workers, --max-files and --max-file-size.
• Non-root AMD64/ARM64 container, Compose and suspended Kubernetes examples, Go/browser-helper CI and existing image-publishing integration.

Validation: local go test -race -cover ./... passes (80.3% coverage), go vet passes, five synthetic browser-helper tests pass, Linux AMD64/ARM64 builds pass, YAML parses and git diff --check passes. The new commit's GitHub Go/browser-helper workflow and AMD64/ARM64 container build both pass.

Live verification: Google login and rendered account pages were verified. The private account API schemas and full export remain unverified after a cloud-browser security-policy block. The partial reference export was saved privately and not committed. Drive is not connected to this conversation and no live Drive publication occurred. Printables free metadata/link generation was verified, but actual file retrieval returned HTTP 403 in this environment. No images were published and no NAS deployment occurred.

Keep this draft until a complete private Drive publication, NAS pull and real file transfer are verified. Further verification/adapters are tracked in #69. Setup and boundaries: three-drop-sync/docs/google-drive-handoff.md; browser workflow: three-drop-sync/agents/README.md.