feat: add private tenant isolation

[steipete-oai]

Summary

• make card and interactive-session ownership private by default with stable subjects
• add expiring named viewer/controller grants, revocation, and read-only terminal/UI behavior
• bind service-created sessions to explicit human owners and recheck authorization around live resources
• scope each agent credential to its authenticated session and direct children
• ship an idempotent migration/backfill path that preserves compatibility triggers through the cutover
• reuse the reviewed libterminal protocol/assets while keeping Crabfleet authorization local

Verification

• 689 Node logic tests
• 3 generated terminal asset tests
• all Go packages
• TypeScript, lint, formatting, Go formatting, and diff checks
• fresh D1 migration, backfill, late-write compatibility, and manual finalizer coverage
• independent autoreview

[clawsweeper]

ClawSweeper status: review started.

I am starting a fresh review of this pull request: feat: add private tenant isolation This is item 1/1 in the current shard. Shard 0/1.

This placeholder means the worker is alive and reading the current context. I will edit this same comment with the actual review when the claws are done clicking.

Crustacean status: shell secured, claws on keyboard, evidence pebbles being sorted.