Add per-session claude token/cost usage panel (WSL, v1)

Reads ~/.claude/projects/*.jsonl transcripts from the open WSL panes'
distros and shows per-session token counts + estimated USD cost, with a
running total in the titlebar.

Backend (src-tauri/src/usage.rs): new get_claude_usage command. For each
distro it probes $HOME once via wsl.exe, reaches the transcripts over the
\\wsl.localhost UNC share, and tallies message.usage per model per
session (summed by each line's model, since a session can switch models).
Results cached by (path,size,mtime) so polling only re-parses the file
that grew; recency-capped (30d / 50 sessions) to bound scan cost.
Windows-only; returns [] elsewhere. quiet_command made pub(crate).

Frontend: src/lib/usage.ts holds the pricing table (per-MTok rates,
matched by model-family substring) + cost/format helpers, so rates are
editable without recompiling Rust. UsagePanel.tsx mirrors the MCP panel
modal; rows whose transcript cwd matches an open pane are highlighted
with a [pane: label] tag. App polls every 20s (visible windows) for the
titlebar 💰 total and every 5s while the panel is open. Ctrl+Shift+U
opens it; added to shortcuts.ts + regenerated README.

tsc clean. Rust builds on the Windows host; needs runtime verification.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/App.tsx

@@ -23,8 +23,10 @@ import {
   createPaneWindow,
   takePendingWindowInit,
   pushWindowWorkspaces,
+  getClaudeUsage,
   type PaneId,
   type SpawnSpec,
+  type SessionUsage,
   type SshHost,
   type McpStatus,
   type McpMirror,
@@ -106,6 +108,8 @@ import Palette from "./components/Palette";
 import HostManager from "./components/HostManager";
 import Help from "./components/Help";
 import McpPanel from "./components/McpPanel";
+import UsagePanel from "./components/UsagePanel";
+import { totalCost, formatUsd } from "./lib/usage";
 import McpConfirm, { type McpConfirmSpec } from "./components/McpConfirm";
 import TabStrip from "./components/TabStrip";
 import "./App.css";
@@ -239,6 +243,9 @@ export default function App() {
     token: null,
   });
   const [mcpPanelOpen, setMcpPanelOpen] = useState(false);
+  const [usagePanelOpen, setUsagePanelOpen] = useState(false);
+  const [usageSessions, setUsageSessions] = useState<SessionUsage[]>([]);
+  const [usageLoading, setUsageLoading] = useState(false);
   const [ready, setReady] = useState(false);
   const [notifications, setNotifications] = useState<Toast[]>([]);
   const [paletteOpen, setPaletteOpen] = useState(false);
@@ -750,6 +757,53 @@ export default function App() {
   const openHostManager = useCallback(() => setHostManagerOpen(true), []);
   const closeHostManager = useCallback(() => setHostManagerOpen(false), []);
 
+  // ---- claude usage tracking ----------------------------------------------
+  // Reads ~/.claude transcripts in the open WSL panes' distros (backend). The
+  // fetch guard collapses overlapping calls (the open panel polls every 5s and
+  // the background heartbeat every 20s both call this).
+  const usageFetchingRef = useRef(false);
+  const refreshUsage = useCallback(async () => {
+    if (usageFetchingRef.current) return;
+    const distros = new Set<string>();
+    for (const leaf of walkLeaves(treeRef.current)) {
+      if (leaf.shellKind === "wsl" && leaf.distro) distros.add(leaf.distro);
+    }
+    if (distros.size === 0) {
+      setUsageSessions([]);
+      return;
+    }
+    usageFetchingRef.current = true;
+    setUsageLoading(true);
+    try {
+      setUsageSessions(await getClaudeUsage(Array.from(distros)));
+    } catch (e) {
+      console.warn("getClaudeUsage failed:", e);
+    } finally {
+      usageFetchingRef.current = false;
+      setUsageLoading(false);
+    }
+  }, []);
+
+  // Background heartbeat so the titlebar total stays roughly current without
+  // the panel open. Gated on visibility so a hidden/minimized window stays quiet.
+  useEffect(() => {
+    const tick = () => {
+      if (document.visibilityState === "visible") void refreshUsage();
+    };
+    tick();
+    const id = window.setInterval(tick, 20000);
+    return () => clearInterval(id);
+  }, [refreshUsage]);
+
+  // cwd + label of open WSL panes, for highlighting matching sessions.
+  const openPanes = useMemo(
+    () =>
+      Array.from(walkLeaves(tree))
+        .filter((l) => l.shellKind === "wsl")
+        .map((l) => ({ cwd: l.cwd ?? "", label: l.label ?? l.distro ?? "pane" })),
+    [tree],
+  );
+
   // Outside-click dismissal for the titlebar dropdowns. Mirrors the
   // per-pane shell-picker pattern in LeafPane.tsx.
   useEffect(() => {
@@ -852,6 +906,14 @@ export default function App() {
         return;
       }
 
+      // Ctrl+Shift+U — usage panel
+      if (ctrl && shift && !alt && key === "u") {
+        e.preventDefault();
+        e.stopPropagation();
+        setUsagePanelOpen((v) => !v);
+        return;
+      }
+
       // Ctrl+Shift+Alt+B — global broadcast all/none
       if (ctrl && shift && alt && key === "b") {
         e.preventDefault();
@@ -2085,6 +2147,14 @@ export default function App() {
         >
           🤖
         </button>
+        <button
+          className="palette-btn usage-btn"
+          onClick={() => setUsagePanelOpen(true)}
+          title="claude token usage & estimated cost (Ctrl+Shift+U)"
+          aria-label="Usage"
+        >
+          💰{usageSessions.length > 0 ? ` ${formatUsd(totalCost(usageSessions))}` : ""}
+        </button>
         <button
           className="palette-btn"
           onClick={() => setHelpOpen(true)}
@@ -2205,6 +2275,16 @@ export default function App() {
         />
       )}
 
+      {usagePanelOpen && (
+        <UsagePanel
+          sessions={usageSessions}
+          loading={usageLoading}
+          onRefresh={refreshUsage}
+          onClose={() => setUsagePanelOpen(false)}
+          openPanes={openPanes}
+        />
+      )}
+
       {confirmQueue.length > 0 && (
         <McpConfirm
           spec={confirmQueue[0]}