MoriRemote: add host-wide agent navigation

[vaayne]

Summary

• add a dedicated Agents scope that aggregates hook-reported states across tmux sessions on the active host
• switch safely across sessions and panes after the target runtime topology arrives
• simplify terminal chrome to Sessions / Agents and remove the intrusive floating notification
• fix tmux control-mode metadata parsing and the empty-state overlay collision

Verification

• iOS Simulator test suite passed, including 224 MoriRemoteTerminal tests
• generic iOS Simulator Release build passed
• verified live tmux hook metadata for Claude and Pi on mbp.local
• git diff --check passed