[rmorehig]

Remove the hidden rtree login --email ... --password ... path and its obsolete selection code. Login continues through browser/device approval or an API key.

Before:

rtree login --email user@example.com --password '...'
# Called POST /v1/auth/login.

After:

rtree login --email user@example.com --password '...'
# Rejected as unsupported arguments.
rtree login
# Opens the existing browser/device approval flow.

The live Platform test now starts CLI device login, approves the emitted code with the local bootstrap session, then checks saved-session access and logout. CI no longer requires a bootstrap password.

Validation: 230 unit/mock tests and all 7 live Platform tests passed; formatting passed. Thermo-nuclear review through P3 found no unresolved issues in scope. An existing unused Duration import warning in commands/insert.rs is unchanged.

Merge this before the companion Platform password-auth removal so Platform's optional CLI compatibility job can use the updated CLI tests from main.

Patch release: bump rawtree-cli from 0.7.4 to 0.7.5 in Cargo.toml and Cargo.lock. Locked offline Cargo metadata validation passed; no dependency changes.