Add Codex Usage plugin

[rayoplateado]

Summary

• Add Codex Usage, a Noctalia bar/panel plugin for Codex usage limits
• Include a 960x540 preview image and required plugin metadata

Details

The plugin uses CodexBar's Linux CLI output:

codexbar usage --provider codex --source cli --format json

It displays the 5-hour and weekly Codex usage windows in the bar and opens a native Noctalia details panel.

Test plan

• python -m json.tool codexbar-usage/manifest.json >/dev/null
• python -m json.tool codexbar-usage/settings.json >/dev/null
• node --check codexbar-usage/codexbar.js
• qmlformat codexbar-usage/*.qml to temp files
• git diff --check

[rayoplateado]

Fixed the code-quality feedback in a85af20 by moving the new user-facing strings to i18n/en.json and replacing the hardcoded QML text/label/description values with pluginApi?.tr(...).

Both checks are now green again.

[smnvdnll]

https://github.com/noctalia-dev/noctalia-plugins/tree/main/model-usage

[spiros132]

What's the difference between this and model-usage?