Replace Shengcai rank with Agent usage rank

[Backtthefuture]

What changed

• replace the Shengcai leaderboard with the public Agent Usage Rank
• auto-link the local Token Rank identity using an allowlist of safe fields
• keep the rank card default-off and avoid local identity/network reads while disabled
• collect WorkBuddy request-level usage without reading message content
• add executable fixture coverage for rank decoding, credential isolation, legacy settings, and WorkBuddy totals
• bump local release defaults to 0.1.46

Privacy

The app only retains public identity fields (id, name, avatar_url, last sync time). It does not decode, persist, or log email, device tokens, source IDs, install tokens, message text, code, or file paths for ranking.

Validation

• ./script/test_ccswitch_proxy_collector.sh
• python3 script/check_localization.py
• ./script/build_swiftui_and_run.sh --verify
• git diff --check
• live public leaderboard matched local user ID 4
• real WorkBuddy collection returned status ok

swift test remains unavailable on this Mac because the local SwiftPM PackageDescription manifest linker is broken; equivalent rank and collector checks run in the standalone fixture.