Support multiple named Context Tree connections

[ggordonhall]

Projects can now attach several named, equal Context Trees. Connecting a second tree adds a connection, discovery and synchronization cover all trees, and writes select one destination with --tree when the project has several connections.

• Add connect --as, create --name --as, selective disconnection, and per-tree sync results that retain successful outcomes when another tree fails.
• Bind prepared writes to their selected connection, update shared checkout references on publication, and scope cleanup schedules, activity, and logs to each tree.
• Update bundled skills, documentation, and package assertions. Changed connection and cleanup schedule contracts use version 2; unchanged responses and tree documents remain version 1. No migration or backwards compatibility layer is included.

Validation: pnpm install, pnpm check, pnpm typecheck, pnpm test (214 tests), and pnpm check:package passed.