Module ids 

ThreadId / SessionId for the crates/core boundary (issue #5261).

Re-exports the protocol ids so every crate that depends on core (the TUI, CLI, app-server) speaks the same typed ids without depending on protocol directly. The persisted JSON shape stays a plain string ("thread-…" / "session-…") so existing state.json / threads/ files need no migration.

Structs

SessionId

One engine session within a thread (a single Op turn or a supervised engine lifetime). Distinct from ThreadId so the thread manager can start a session with no TUI attached and so tests can assert headless == TUI byte-identical requests for the same ThreadId + SessionId pair.

ThreadId

Long-lived conversation id. Backwards compatible with the existing thread-{uuid} string form used in crates/state and runtime_threads.