Add an editor context menu for selected text

[Arham Amin (arhxam)]

Fixes #854.

Summary

Right-clicking inside the current text selection now opens a small in-editor context menu with Cut, Copy, Paste, Select All, and Find. The menu reuses Edit's existing command, localization, clipboard, and TUI menu primitives, so the actions behave the same as their Edit-menu and keyboard-shortcut equivalents.

The popup follows the click position, flips toward the viewport when opened near the right or bottom edge, supports normal keyboard focus, and closes on Escape, command activation, or focus loss. Right-clicks outside a selection keep the existing behavior.

Test plan

• cargo test -p edit --bin edit draw_editor::tests::right_clicking_selected_text_opens_context_menu -- --nocapture
• cargo test --workspace
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings

The regression test creates a real selection, delivers a right-mouse event through the TUI input path, and verifies the rendered popup contains each requested localized command.

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[Leonard Hecker (lhecker)]

I like the idea of this PR overall, but this addition is not suistainable long-term. Eventually (and I mean: in the near-term) this would need to be rewritten as other features are added. A different approach is required that allows for capturing right-clicks.

I was actually thinking about this lately because I do not like how the input system works right now. I found AI somewhat unhelpful in my quest to find a different approach FYI. One idea I had was to model the input event API somewhat loosely around how browser key and mouse events work. The question is how to marry that with an immediate mode UI.