fix(frontend): load sweep-shared.css once from main.ts — a shared <style src> breaks vite build (#3207)

plugin-vue throws "Cannot read properties of undefined (reading 'scoped')"
when several SFCs share one src stylesheet. vue-tsc passed, so only the
image job caught it; :dev has not rebuilt since 22b7a92.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/assets/sweep-shared.css

@@ -6,7 +6,7 @@
  * right, a small grid of facts, and a row of plain buttons. It was written
  * out four times, scoped, before this sheet existed.
  *
- * Imported UNSCOPED (`<style src="@/assets/sweep-shared.css" />`), so every
+ * Imported UNSCOPED, once, from main.ts, so every
  * class is prefixed `sweep-`: `.row-title`, `.lede`, `.age` and `.actions`
  * also exist, scoped, in views that have nothing to do with sweeps, and an
  * unprefixed global would leak into all of them. What a pane does

frontend/src/components/NoteSweepPane.vue

@@ -149,4 +149,3 @@ h2 { margin: 0; font-size: 1.05rem; }
 /* A check can be a long URL or command with no break point. */
 .sweep-check dd { overflow-wrap: anywhere; }
 </style>
-<style src="@/assets/sweep-shared.css" />

frontend/src/components/rules/PreferenceDriftPane.vue

@@ -194,4 +194,3 @@ onMounted(() => store.fetchDrift());
    row of facts. */
 .sweep-actions { align-items: baseline; gap: var(--fs-space-3); flex-wrap: wrap; margin-top: 0; }
 </style>
-<style src="@/assets/sweep-shared.css" />

frontend/src/components/rules/RuleHistoryPanel.vue

@@ -269,4 +269,3 @@ watch(() => props.ruleId, () => { selected.value = null; load(); });
 }
 h4 { margin: var(--fs-space-2) 0 0; font-size: var(--fs-size-tiny); color: var(--fs-text-tertiary); }
 </style>
-<style src="@/assets/sweep-shared.css" />

frontend/src/components/rules/RuleSweepPane.vue

@@ -124,4 +124,3 @@ onMounted(reload);
   overflow-wrap: anywhere;
 }
 </style>
-<style src="@/assets/sweep-shared.css" />

frontend/src/main.ts

@@ -6,6 +6,9 @@ import "./assets/theme.css";
 // After theme.css — it consumes the tokens declared there.
 import "./assets/components.css";
 import "./assets/prose.css";
+// Global rather than `<style src>` per pane: plugin-vue cannot compile one
+// src stylesheet shared by several SFCs (#3207 broke the image build).
+import "./assets/sweep-shared.css";
 
 const app = createApp(App);
 app.use(createPinia());