Mac status bar controls for Codexplain explanation UX

[minsing-jin]

Goal

Add a macOS status bar controller for Codexplain so users can turn the project-local Codexplain integration on/off and adjust explanation levels without editing config files or running multiple commands.

User story

As a Codexplain user, while using Codex, I want a small macOS menu bar control where I can enable/disable Codexplain and choose how Codex explains things, so I can switch between code-level, architectural, abstract, and metaphorical explanations quickly.

Scope

• Add a macOS status bar/menu bar controller.
• Toggle Codexplain on/off for the current project-local integration.
• Reflect whether .codexplain/activate / project-local shim is active where technically detectable.
• Preserve clean uninstall behavior: removing or turning off Codexplain must remove only Codexplain-managed files/blocks and must not touch unrelated Codex settings.
• Provide level controls for explanation style.

Proposed controls

• Power: on/off
• Explanation depth: light / standard / deep
• Architecture depth: overview / system / internals
• Abstraction level: concrete / architecture / strategy
• Expression mode: code-based / conceptual / metaphorical
• Color output: ansi / plain / html-chat
• Theme: ocean / forest / warm / sunset / grape / slate / rose / mono

UX requirements

• Show current state in the menu bar.
• Make changes write through to Codexplain profile/config, not global unrelated Codex config.
• Provide a one-click restore/off path.
• Keep all existing strict-output safety: JSON, code, diffs, logs, test output, and commit messages must remain unchanged.

Architecture note

The control should be a thin UI over the existing Rust CLI commands, not a second renderer implementation. It should call or reuse Codexplain commands for install, uninstall, profile, and style management.

Acceptance criteria

• User can enable/disable Codexplain from the macOS status bar.
• User can adjust the 3-stage depth controls from the status bar.
• User can choose code/concept/metaphor explanation mode.
• Turning off restores the previous Codex behavior and removes only Codexplain-managed integration files/blocks.
• Tests or scripted checks prove that unrelated Codex settings remain untouched.