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/routes/+layout.svelte

@@ -22,6 +22,7 @@
   import { listen } from "@tauri-apps/api/event";
   import { toasts } from "$lib/stores/toasts.svelte.js";
   import { initI18n } from "$lib/i18n";
+  import { refreshLlmStatus } from "$lib/stores/llmStatus.svelte.js";
 
   import { page as sveltePage } from "$app/stores";
 
@@ -301,6 +302,12 @@
       })
       .catch(() => { /* update check failure must not affect the app */ });
 
+    // Seed the LLM status chip (sidebar) with whichever state the
+    // backend is in right now. The chip also reacts to the $effect
+    // on settings.aiTier below and to explicit mark-generating
+    // calls from DictationPage around cleanup_transcript_text_cmd.
+    refreshLlmStatus(settings.aiTier).catch(() => {});
+
     // Meeting auto-capture: poll the process list and toast when a match
     // appears (edge-triggered — no repeat toasts until the app goes away
     // and comes back). We never start recording from this signal; the