Add niri-animations plugin

[ImJustDoingMyPart]

Plugin

• Id: imjustdoingmypart/niri-animations
• New plugin
• Update to an existing plugin (version bumped in plugin.toml)

What it does

Lets you switch niri animation presets from a Noctalia panel instead of editing config and
reloading the compositor by hand.

The plugin owns one file — ~/.config/niri/animations.kdl by default — and rewrites it with
an include for the chosen preset plus an animations block carrying the global speed:

include "./animations/prism_fold.kdl"

animations {
    slowdown 1.50
}

Then it runs the reload command. It never touches config.kdl; that file is expected to
include the target file last, after your base animations.

The panel offers a preset dropdown (plus No preset, which falls back to your base pack), an
on/off toggle, a 0.25×–3.00× speed slider, and a Random button. Two panel entries ship the
same script with different anchoring — picker floating and docked attached to the bar —
because placement is host-owned and cannot be changed at runtime or overridden by the user.
A control-center tile opens the attached one and highlights while animations are enabled.

Presets are listed by filename on purpose: preset headers carry a free-form Desc: field
that is frequently just "imported from https://…", and surfacing it makes the plugin look
broken when the problem is somebody else's metadata.

External dependencies

niri — used for the reload command (niri msg action load-config-file, configurable).
Declared in dependencies in plugin.toml. No other external commands, and no network
access.

Testing

Exercised on a live session against 19 presets:

• Opened both panels via IPC (panel-toggle …:picker and …:docked) and confirmed each
  registers and renders.

• Picked presets from the dropdown, toggled animations off and on, moved the speed slider,
  and used Random — verifying each writes the target file and that niri reloads.

• Confirmed the panel reopens reflecting the on-disk state (selected preset, speed, on/off)
  after external edits to the target file.

• Validated all three generated shapes (preset + slowdown, no preset + slowdown, off)
  with niri validate against a full config tree.

• Verified the control-center tile reflects the enabled/disabled state.

• Tested on Niri

• Tested on Hyprland

• Tested on Sway

• Tested on another compositor:

• Noctalia version tested against: 5.0.0-beta.7 (noctalia v5.0.0 (97917d9ca07e))

• Plugin API level: 9

On plugin_api: I set 9 to match the official example plugin, which demonstrates the same
entry types (panels with the declarative ui.* vocabulary, plus a shortcut). The docs don't
state which level first shipped ui.select, listDir/writeFile/runAsync, or root-level
[[setting]], so I could not derive the true minimum. Happy to lower it if a reviewer knows
it should be lower.

Screenshots / Videos

thumbnail.webp in this PR embeds a live capture of the picker panel (preset dropdown on
tv_crt, speed at 1.00×, 19 presets discovered). Full-resolution screenshots of both the
floating and bar-attached variants follow in a comment.

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

• 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.

[ImJustDoingMyPart]