fix(blocklist): render llm_score, fix load() error handling, fix severity override mutations

- BlocklistView: display llm_score/llm_reason when non-null (spec gap)
- BlocklistView: set scanError on non-ok load() response (was silent)
- SettingsView: replace in-place splice/property mutation with immutable
  spread pattern in toggleOverride/deleteOverride

web/src/views/BlocklistView.vue

@@ -130,6 +130,12 @@
               </template>
             </div>
 
+            <!-- LLM score (Premium tier stub) -->
+            <div v-if="c.llm_score !== null" class="mt-1 text-xs text-text-dim">
+              <span class="font-medium">LLM score:</span> {{ c.llm_score?.toFixed(2) }}
+              <span v-if="c.llm_reason" class="ml-2 text-text-dim/70">— {{ c.llm_reason }}</span>
+            </div>
+
             <!-- Log evidence -->
             <div v-if="c.log_evidence.length" class="mt-1">
               <button
@@ -226,7 +232,11 @@ async function load() {
   loading.value = true
   try {
     const res = await fetch(`${BASE}/api/blocklist/candidates`)
-    if (res.ok) candidates.value = (await res.json()).candidates
+    if (res.ok) {
+      candidates.value = (await res.json()).candidates
+    } else {
+      scanError.value = `Failed to load candidates: ${res.statusText}`
+    }
   } finally {
     loading.value = false
   }

web/src/views/SettingsView.vue

@@ -372,13 +372,20 @@ async function saveOverrides() {
 }
 
 async function toggleOverride(i: number) {
-  const rule = prefs.value.severity_overrides[i]
-  if (rule) rule.enabled = !rule.enabled
+  prefs.value = {
+    ...prefs.value,
+    severity_overrides: prefs.value.severity_overrides.map((r, idx) =>
+      idx === i ? { ...r, enabled: !r.enabled } : r
+    ),
+  }
   await saveOverrides()
 }
 
 async function deleteOverride(i: number) {
-  prefs.value.severity_overrides.splice(i, 1)
+  prefs.value = {
+    ...prefs.value,
+    severity_overrides: prefs.value.severity_overrides.filter((_, idx) => idx !== i),
+  }
   await saveOverrides()
 }