fix(terminal): restore clipboard shortcuts and suppress ask popup

[viniraioli]

What

Restore standard clipboard behavior in terminal and coding-agent sessions, and prevent the Ask Agent selection popup from appearing outside editor tabs.

Why

Windows users currently lose Ctrl+V inside coding agents, and Ctrl+C sends SIGINT even when terminal text is selected. The Ask Agent popup also overlaps copy actions on terminal selections. Closes #240.

How

• Intercept terminal clipboard shortcuts by platform so copy prefers the current terminal selection and Windows Ctrl+V reads from the system clipboard.
• Route DOM paste events on the xterm host through erm.paste(...).
• Clear the Ask Agent popup unless the active tab is an editor.

Testing

• pnpm exec tsc --noEmit clean
• Manual smoke-test of the affected feature
• (If you touched src-tauri/) cargo check clean
• (If UI) tested in pnpm tauri dev

Screenshots / GIFs

N/A - behavior-only UI change.

Notes for reviewer

I did not run a full manual Windows smoke test in pnpm tauri dev; this is validated by typecheck and targeted code inspection against the issue #240 repro steps.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates terminal and app selection behavior by improving platform-specific keyboard handling and clipboard integration.

Changes:

• Add a custom xterm addon + shortcut handler to support terminal copy/paste behavior.
• Switch Ctrl+Backspace modifier detection to use platform constants instead of UA sniffing.
• Prevent the “Ask” popup from persisting when the active tab is not the editor.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/modules/terminal/lib/rendererPool.ts	Adds terminal clipboard handling (paste addon + copy/paste shortcuts) and improves platform modifier detection.
src/app/App.tsx	Uses a ref for current tab kind to close the ask popup when not in the editor tab.

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