Add an optional limited editor mode

[moon-jam]

Add five independent editor options below Difficulty: syntax highlighting, code execution, automatic indentation, bracket auto-close, and monospace font. All are enabled by default. Choices survive lobby reloads and are captured when an interview starts; existing links retain the default behavior.

The editor applies these settings while preserving native undo/redo, manual indentation, and line numbers. Parser assets load only when automatic indentation or bracket highlighting needs them.

When code execution is disabled, Run and its keyboard shortcuts are disabled, and all five languages remain available. The interviewer asks candidates to trace their written code through ordinary and boundary cases instead of requesting a run. Execution events cannot earn Test credit, the hiring bar remains unchanged, and saved and exported reports disclose the restriction. The live and report prompt changes are recorded under contract bundle 31.

Closes #73
Closes #85

---

Summary by cubic

Adds five independent lobby editor options below Difficulty — syntax highlighting, code execution, automatic indentation, bracket auto-close, and monospace font — all enabled by default. Choices survive lobby reloads, are captured when an interview starts, and existing links keep every feature on.

Editor options

• The editor applies each setting while preserving native undo/redo, manual indentation, and line numbers.
• Parser assets load only when automatic indentation or bracket highlighting needs them.

Disabled code execution

• Run and its keyboard shortcuts are disabled while all five languages stay selectable, and the interviewer asks candidates to hand-trace their code instead; whiteboard sessions ignore the choice because they have no code runner.
• Execution events cannot earn Test credit, and saved and exported reports disclose the restriction.
• Live and report prompt changes are recorded under contract bundle 31.

^{Written for commit 48b11b4. Summary will update on new commits.}