Relay v0.20.0

Features

• sessions: deactivate an agent session, keeping the way back

Fixes

• agent-runtime: point a surface's hooks at the instance that owns it
• terminal: close the pty session when a surface is torn down

Other

• record Cycle 26, rotate cycles 9-11, prune the roadmap
• readme: mention session deactivation
• guide: explain deactivating a session
• app: move the window title and chrome observers next to the windows
• drop the saved transcript from the deactivation plan
• model: drop the unused adoptTab
• write down who owns a tab's pty session
• record the pty teardown leak and plan the fix
• guide: explain resumes that hit a waiting shell prompt

Full Changelog: v0.19.0...v0.20.0