feat(sidebar B.1 #31): visible LLM status chip with live state

The LLM runtime has been quiet since it shipped in Phase 3 — users
had no surface-level signal that cleanup was loaded, warming, or
actively generating. Settings has verbose status text internally,
but a dictation-flow user never opens Settings during a run.

New: a shared $state store drives a small chip in the sidebar that
reflects the true LLM state in ≤500 ms of any transition (brief
item #31 acceptance). Five states:

  off        → hidden (user has aiTier === "off")
  warming    → model download or first load in flight; amber pulse
  ready      → loaded + idle; green dot
  generating → cleanup_transcript_text_cmd or
               extract_tasks_from_transcript_cmd in flight; accent
               pulse with Sparkles icon
  error      → last operation failed; red dot with AlertTriangle

The store exposes three calls: refreshLlmStatus(aiTier) (polls the
backend), markGenerating(detail) / markGenerationDone(success).
DictationPage wraps its cleanup + extract calls in mark-generating
pairs. SettingsPage's LLM load / unload / delete / download paths
also refresh the global store so Settings-initiated transitions
surface in the sidebar immediately. The chip collapses to a
dot-only compact form when the sidebar is collapsed.

No backend changes — everything wires onto the existing
`get_llm_status` Tauri command.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/components/LlmStatusChip.svelte

@@ -0,0 +1,60 @@
+<script lang="ts">
+  // @ts-nocheck
+  import { Sparkles, AlertTriangle } from "lucide-svelte";
+  import { llmStatus } from "$lib/stores/llmStatus.svelte.js";
+
+  let { compact = false } = $props<{ compact?: boolean }>();
+
+  let label = $derived.by(() => {
+    switch (llmStatus.kind) {
+      case "warming":
+        return llmStatus.detail ?? "AI warming";
+      case "ready":
+        return "AI ready";
+      case "generating":
+        return llmStatus.detail ?? "Cleaning…";
+      case "error":
+        return "AI error";
+      default:
+        return "";
+    }
+  });
+
+  let dotClass = $derived.by(() => {
+    switch (llmStatus.kind) {
+      case "warming":
+        return "bg-warning animate-pulse";
+      case "ready":
+        return "bg-success";
+      case "generating":
+        return "bg-accent animate-pulse";
+      case "error":
+        return "bg-danger";
+      default:
+        return "bg-text-tertiary";
+    }
+  });
+</script>
+
+{#if llmStatus.kind !== "off"}
+  {#if compact}
+    <span
+      class="inline-flex items-center justify-center w-[10px] h-[10px] rounded-full {dotClass}"
+      title={label}
+      aria-label={label}
+    ></span>
+  {:else}
+    <span
+      class="inline-flex items-center gap-1.5 px-2 py-[3px] rounded-full bg-bg-elevated border border-border-subtle text-[10px] text-text-secondary whitespace-nowrap"
+      title={llmStatus.detail ?? label}
+    >
+      <span class="inline-block w-[6px] h-[6px] rounded-full {dotClass}"></span>
+      {#if llmStatus.kind === "error"}
+        <AlertTriangle size={10} class="text-danger" />
+      {:else if llmStatus.kind === "generating"}
+        <Sparkles size={10} class="text-accent" />
+      {/if}
+      <span>{label}</span>
+    </span>
+  {/if}
+{/if}