fix: restore terminal focus after context menu dismiss

[AllBeingsFuture]

Summary

Follow-up fix for #2948 review findings:

• Restore xterm focus on any context-menu dismiss (Escape / outside click / action), not only after menu item actions
• Align Clear with CLEAR_SEQUENCE used by AttachableTerminal.clear
• Tests: Escape dismiss refocuses terminal; Copy enabled when selection exists

Tests

• npx -y node@22.12.0 ./node_modules/vitest/vitest.mjs run --config vite.renderer.config.ts XtermTerminal.test.tsx (40 passed)
• npm run typecheck (frontend)

Stacked onto #2948 head branch because this account cannot push to AgentWrapper/agent-orchestrator directly.

[somewherelostt]

Thanks for contributing to Agent Orchestrator.

This PR is being picked up by the current external contributor on-call pair:

• @illegalcall
• @Pulkit7070

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[AllBeingsFuture]

Closing as superseded by #2966 (correct tip / base on main after #2948). Keeper is #2966.