Remove auto-compile toggle and compile button from playground

[Mossaka]

Summary

• Removes the "Auto" toggle switch and "Compile" button from the playground editor header
• Removes the Ctrl+Enter keyboard shortcut hint from the editor panel
• Removes all related CSS (toggle switch styles) and JS (autoCompile state, toggle listener, button references)
• Compilation now always happens automatically on input change with 400ms debounce
• The Ctrl/Cmd+Enter keymap is retained as a shortcut for immediate compilation

Test plan

• Open the playground editor and verify the Auto toggle and Compile button are gone
• Type in the editor and confirm output auto-compiles after a brief delay
• Press Ctrl+Enter (or Cmd+Enter on Mac) and confirm immediate compilation still works
• Toggle light/dark theme and verify it still works (theme button is the only remaining header control)
• Test on mobile viewport to ensure responsive layout still works

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR simplifies the playground editor by removing manual compilation controls and making compilation always automatic. The changes remove unnecessary UI complexity while maintaining the ability to manually trigger compilation via keyboard shortcut.

Changes:

• Removed "Auto" toggle switch, "Compile" button, and Ctrl+Enter hint from the editor header
• Removed all related CSS for toggle switch styling and responsive behavior
• Removed autoCompile state management and related event listeners from JavaScript
• Compilation now always occurs automatically with 400ms debounce when the editor content changes

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/public/editor/index.html	Removed toggle switch and compile button UI elements from header, removed related CSS styles, and removed keyboard shortcut hint from editor panel
docs/public/editor/editor.js	Removed DOM references for compile button and toggle, removed autoCompile state and toggle listener, simplified update listener to always trigger auto-compile, and updated init function to unconditionally compile default content

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