Polish for shipping: robust auto-detect, empty state, real icons, end-user README

- cli_usage::default_command now enumerates WSL distros and probes each for
  claude before falling back; no more hardcoded -d Ubuntu.
- New autodetect_claude_command Tauri command + IPC binding so the UI knows
  whether claude is reachable.
- App.svelte: clear 'Claude Code not found' empty state with install link.
- Real icons: scripts/make-icon.py generates a 1024x1024 source.png; runtime
  produces 32/128/256 PNGs and a multi-resolution .ico. README in icons/
  explains how to regen.
- README rewritten for friends: install / requirements / troubleshooting on
  top; build-from-source moved to bottom.

src/components/App.svelte

@@ -7,6 +7,8 @@
     getCliUsage,
     onCliUsageUpdated,
     refreshCliUsage,
+    autodetectClaudeCommand,
+    getSettings,
   } from "../ipc";
   import TitleBar from "./TitleBar.svelte";
   import BlockRing from "./BlockRing.svelte";
@@ -18,6 +20,8 @@
   let cliUsage = $state<CliUsage | null>(null);
   let cliRefreshing = $state(false);
   let showSettings = $state(false);
+  /** True when Claude Code can't be found anywhere on this machine. */
+  let claudeMissing = $state(false);
 
   let unlisten1: (() => void) | null = null;
   let unlisten2: (() => void) | null = null;
@@ -40,9 +44,18 @@
       console.error("listen failed", e);
     }
 
-    // If we have nothing yet, fire a one-shot refresh so the widget is
-    // useful right away rather than waiting for the 5-min loop.
-    if (!cliUsage) {
+    // Probe whether claude is reachable at all.
+    try {
+      const settings = await getSettings();
+      const hasOverride = !!(settings.claude_command && settings.claude_command.trim());
+      const auto = await autodetectClaudeCommand();
+      claudeMissing = !hasOverride && !auto;
+    } catch (e) {
+      console.warn("autodetect probe failed", e);
+    }
+
+    // Trigger an initial refresh if we have nothing AND claude is reachable.
+    if (!cliUsage && !claudeMissing) {
       void triggerRefresh();
     }
   });
@@ -71,19 +84,38 @@
   refreshing={cliRefreshing}
 />
 
-<BlockRing bar={cliUsage?.session ?? null} />
+{#if claudeMissing}
+  <div class="empty-state">
+    <div class="title">Claude Code not found</div>
+    <p>
+      This widget reads your subscription usage by running
+      <code>claude /usage</code>. Install Claude Code first, then sign in.
+    </p>
+    <p>
+      <a href="https://docs.claude.com/en/docs/claude-code" target="_blank" rel="noopener">
+        Install Claude Code →
+      </a>
+    </p>
+    <p class="hint">
+      Already installed? Open Settings and set <em>claude command</em>
+      (e.g. <code>wsl.exe -d Ubuntu bash -lc claude</code>).
+    </p>
+  </div>
+{:else}
+  <BlockRing bar={cliUsage?.session ?? null} />
 
-<ModelStack
-  breakdown={snap?.block?.by_family ?? snap?.weekly.by_family ?? { opus: 0, sonnet: 0, haiku: 0, other: 0 }}
-/>
+  <ModelStack
+    breakdown={snap?.block?.by_family ?? snap?.weekly.by_family ?? { opus: 0, sonnet: 0, haiku: 0, other: 0 }}
+  />
 
-<WeeklyBar
-  weekAll={cliUsage?.week_all ?? null}
-  weekSonnet={cliUsage?.week_sonnet ?? null}
-/>
+  <WeeklyBar
+    weekAll={cliUsage?.week_all ?? null}
+    weekSonnet={cliUsage?.week_sonnet ?? null}
+  />
 
-{#if cliRefreshing && !cliUsage}
-  <div class="loading">Reading /usage…</div>
+  {#if cliRefreshing && !cliUsage}
+    <div class="loading">Reading /usage…</div>
+  {/if}
 {/if}
 
 {#if showSettings}
@@ -98,4 +130,30 @@
     font-size: 12px;
     text-align: center;
   }
+  .empty-state {
+    flex: 1 1 0;
+    display: flex;
+    flex-direction: column;
+    justify-content: center;
+    padding: 12px var(--pad);
+    gap: 6px;
+    color: var(--fg);
+    font-size: 12px;
+  }
+  .empty-state .title {
+    color: var(--fg);
+    font-weight: 600;
+    text-align: center;
+    margin-bottom: 4px;
+  }
+  .empty-state p { margin: 0; line-height: 1.4; }
+  .empty-state .hint { color: var(--fg-dim); font-size: 11px; }
+  .empty-state a { color: var(--accent); text-decoration: none; }
+  .empty-state a:hover { text-decoration: underline; }
+  .empty-state code {
+    background: var(--bg-card);
+    padding: 1px 4px;
+    border-radius: 3px;
+    font-size: 11px;
+  }
 </style>

src/ipc.ts

@@ -19,6 +19,8 @@ export const quitApp = (): Promise<void> => invoke("quit_app");
 export const detectPlanTier = (): Promise<TierInfo> => invoke("detect_plan_tier");
 export const getCliUsage = (): Promise<CliUsage | null> => invoke("get_cli_usage");
 export const refreshCliUsage = (): Promise<CliUsage> => invoke("refresh_cli_usage");
+export const autodetectClaudeCommand = (): Promise<string[] | null> =>
+  invoke("autodetect_claude_command");
 
 export const onUsageUpdated = (
   cb: (snap: UsageSnapshot) => void,