Tab Cleanup

IAB tabs persist for the lifetime of the current ZCode process. Turn end, session end, an omitted finalize call, and omission from keep do not close a tab.
Call tab.close() only when the model intentionally decides to close that exact tab. A user may also close tabs directly in the UI.
browser.tabs.finalize({ keep }) is a lifecycle-marking operation, not a cleanup allowlist. Listed tabs become deliverable or handoff; unlisted tabs retain their current lifecycle and remain visible.
Use deliverable when a live page is the requested result and should be released from agent control. Use handoff when unfinished work must remain controllable by the same session.
ZCode does not restore these tabs after the ZCode process exits.