Cross-device session sync: resume a Claude Code session on a different machine

Problem
I work across two devices (desktop + laptop). Sessions live locally on each machine, so when I switch devices I either (a) lose session context entirely, (b) manually copy transcripts, or (c) re-describe what I was doing. Auto-memory helps with long-term prefs, but not with in-flight work.

Proposal
Opt-in cloud sync for session transcripts + plan files + auto-memory, keyed to my Anthropic account. On a second device, claude --resume <session-id> (or a session picker) pulls the state and I continue where I left off. Local-only should remain the default for privacy; sync is an explicit toggle per repo or globally.

Why it matters
Hopping between devices is the normal working pattern for a lot of users. Not being able to resume is a sharp edge that pushes people to stay on one machine or start over.