feat: add presence option for plan mode auto switch

[Raymond8196]

Summary

Adds a user-presence–aware option controlling the plan-mode auto-switch behavior. When the auto-switch-to-plan policy fires, it now respects the current user presence state so the mode switch is only auto-suggested/applied in the appropriate presence context.

Changes

• Backend (agent-core)
  • mode_switch.rs / presence_policy.rs: thread presence state into the auto-switch decision.
  • session/types/context.rs: carry presence in session context.
  • orchestration/suggest_mode_switch.rs: honor the presence policy when suggesting a mode switch.
• Frontend
  • settingsSchema/registry/agent.ts + integrations.ts: new configurable presence option.
  • ModeSwitchCard/useModeSwitchActions.ts, mode-switch/index.tsx, toolHandlers.ts: wire the option through the mode-switch UI/event path.
  • userPresenceAtom.ts + types/userPresence.ts + MyRole / MyRolesSection: presence state store and role UI.

Tests

• createPlanFinalization.test.ts and userPresenceAtom.test.ts updated/extended.
• Pre-commit hook: eslint 0, circular 0.