Fix paste into Monaco find widget

[wargoblin]

Fixes #115.\n\n## Summary\n- Scope Markpad's custom Monaco copy shortcut to editor text focus.\n- Scope the custom paste command to editor text focus so Monaco's find widget keeps native clipboard handling.\n\n## Test plan\n- npm run check\n- cargo check\n- cargo test\n- Internal review PR CI passed: https://github.com/wargoblin/Markpad/actions/runs/25441558927\n- Isolated Monaco smoke test: with find widget focused, custom paste/copy handlers do not run; with editor text focused, they still run.

[Copilot]

Pull request overview

Scopes Markpad’s custom Monaco clipboard keybindings (Ctrl/Cmd+C and Ctrl/Cmd+V) to only apply when the editor text area is focused, restoring native clipboard behavior for Monaco UI widgets like the Find widget (fixing #115).

Changes:

• Restricts the custom copy action (custom-copy) to editorTextFocus so it won’t intercept copy in non-editor inputs (e.g., Find widget).
• Restricts the custom paste command (Ctrl/Cmd+V) to editorTextFocus so pasting into the Find widget uses Monaco’s native handling.

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[wargoblin]

Hi @alecdotdev, this PR fixes #115 by scoping Markpad's custom Monaco clipboard shortcuts to editor text focus, so the find widget keeps native copy/paste while editor paste behavior stays unchanged.\n\nPre-submit checklist:\n- Rebasing/preflight: one commit on top of current upstream/master; diff limited to src/lib/components/Editor.svelte.\n- Local checks: npm run check passed with 0 errors (existing 14 Svelte warnings unchanged); cargo check and cargo test passed (existing APP_NAME warning unchanged).\n- Review: internal Codex, Copilot, and Claude review completed with no actionable code comments; added isolated Monaco smoke tests for find-widget copy/paste and editor-focused copy/paste behavior.\n- GitHub Actions: upstream CI passed.\n\nReady to adjust if you prefer a narrower clipboard-scope policy.

[alecdotdev]

great stuff, thanks!