chore(ui): refactor workspace to monorepo (#70)

## Summary by Sourcery

Refactor the UI project structure into a pnpm monorepo packages layout
and align tooling and automation with the new paths.

Enhancements:
- Reorganize the UI app from the root ui directory into packages/ui
within a pnpm workspace.
- Update pnpm workspace configuration to include all packages under
packages/*.
- Adjust paths in changeset configuration so the @dropout/ui package
resolves from packages/ui.

Build:
- Update pre-commit configuration paths and arguments to reflect the new
UI location and normalize hook argument formatting.
- Update Dependabot configuration so npm updates target /packages/ui
instead of /ui.

CI:
- Update GitHub Actions workflows to watch packages/** instead of ui/**
and to run frontend tasks from packages/ui.
- Update pnpm cache dependency paths in workflows to use the root
pnpm-lock.yaml.
- Simplify frontend install steps in test workflows to run from the
repository root.

Chores:
- Add a new index.html under packages/ui and remove the old
ui/index.html to match the new project layout.

1 files changed, 0 insertions, 70 deletions

diff --git a/ui/src/components/ParticleBackground.svelte b/ui/src/components/ParticleBackground.svelte
deleted file mode 100644
index 7644b1a..0000000
--- a/ui/src/components/ParticleBackground.svelte
+++ /dev/null
@@ -1,70 +0,0 @@
-<script lang="ts" module>
-  import { SaturnEffect } from "../lib/effects/SaturnEffect";
-  
-  // Global reference to the active Saturn effect for external control
-  let globalSaturnEffect: SaturnEffect | null = null;
-  
-  export function getSaturnEffect(): SaturnEffect | null {
-    return globalSaturnEffect;
-  }
-</script>
-
-<script lang="ts">
-  import { onMount, onDestroy } from "svelte";
-  import { ConstellationEffect } from "../lib/effects/ConstellationEffect";
-  import { settingsState } from "../stores/settings.svelte";
-
-  let canvas: HTMLCanvasElement;
-  let activeEffect: any;
-
-  function loadEffect() {
-    if (activeEffect) {
-      activeEffect.destroy();
-    }
-    
-    if (!canvas) return;
-
-    if (settingsState.settings.active_effect === "saturn") {
-      activeEffect = new SaturnEffect(canvas);
-      globalSaturnEffect = activeEffect;
-    } else {
-      activeEffect = new ConstellationEffect(canvas);
-      globalSaturnEffect = null;
-    }
-    
-    // Ensure correct size immediately
-    activeEffect.resize(window.innerWidth, window.innerHeight);
-  }
-
-  $effect(() => {
-    const _ = settingsState.settings.active_effect;
-    if (canvas) {
-        loadEffect();
-    }
-  });
-
-  onMount(() => {
-    const resizeObserver = new ResizeObserver(() => {
-      if (canvas && activeEffect) {
-         activeEffect.resize(window.innerWidth, window.innerHeight);
-      }
-    });
-    
-    resizeObserver.observe(document.body);
-    
-    return () => {
-      resizeObserver.disconnect();
-      if (activeEffect) activeEffect.destroy();
-    };
-  });
-  
-  onDestroy(() => {
-    if (activeEffect) activeEffect.destroy();
-    globalSaturnEffect = null;
-  });
-</script>
-
-<canvas
-  bind:this={canvas}
-  class="absolute inset-0 z-0 pointer-events-none"
-></canvas>