fix(editor): enforce spellcheck toggle on CodeMirror contenteditable

[nicepopo86-lang]

Summary

This fixes editor spellcheck toggle behavior for the CodeMirror contenteditable input.

What changed

• Ensure spellcheck is applied directly to CodeMirror's input field (getInputField()).
• Apply autocorrect and autocapitalize attributes consistently with the toggle state.
• Re-apply attributes both on editor mount and whenever config updates.

Why

The settings toggle (general.enableSpellcheck) existed, but browser spellcheck behavior could still fail to reflect runtime state in contenteditable mode.

Scope

• No API changes
• No schema changes
• Frontend editor behavior only

Related issue: #695

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