Add Quick Shell plugin for launcher commands

[weinguyen1224-glitch]

Introduces /qs launcher prefix to run shell commands in an interactive terminal. Features dynamic shell completions (Fish/Bash), command history, user snippets, and directory navigation.

Plugin

• Id: <author>/<plugin>
• New plugin
• Update to an existing plugin (version bumped in plugin.toml)

What it does

External dependencies

Testing

• Tested on Niri
• Tested on Hyprland
• Tested on Sway
• Tested on another compositor:
• Noctalia version tested against:
• Plugin API level:

Screenshots / Videos

Checklist

• The directory name matches the part of id after the / in plugin.toml exactly.
• It ships plugin.toml, README.md, thumbnail.webp, and translations/en.json.
• README.md follows the
  README template, documents
  every entry id and dependency, and includes exact panel IPC commands and launcher prefixes where applicable.
• I created thumbnail.webp with the thumbnail generator.
• version follows semver and is bumped in this PR; plugin_api is the oldest API level this plugin requires.
• Every non-English translation in this PR uses a locale supported by Noctalia core, and I can read, write, and
  understand that language well enough to review and maintain it (no unreviewed machine/LLM translations).
• I did not edit catalog.toml; CI generates it.
• This PR touches exactly one plugin directory.

Code review attestation

Plugins run as trusted, unsandboxed Luau in the user's session. Confirm:

• The code is readable and not obfuscated, minified, or generated.
• It does not download and execute remote code.
• Every network call, filesystem write, and spawned process is something the description above accounts for.
• I have the right to publish this code under the license declared in plugin.toml.

[jinliu]

The naming could be a bit unfortunate, as older versions of Noctalia is based on Quickshell, and the command name is "qs". So this could lead to confusion.

How about "Shell Command" and "/sh"?