fix(desktop): dedupe Linux tray D-Bus calls to stop main-thread freeze (#2459)

The tray controller called setToolTip and setContextMenu unconditionally on
every snapshot push. On Linux both are synchronous D-Bus calls into
plasmashell's StatusNotifierItem host. useTraySync debounced pushes at 120ms
(up to ~8/sec during token streaming), so each push made 2 blocking D-Bus
round-trips even when only dockBadgeCount changed or a token streamed into
an already-listed session — i.e., tooltip and menu content didn't change.
The native block has no JS-level log, is intermittent (depends on plasmashell
load), and eventually freezes the Electron main thread until crash.

setTitle and setImage were already deduped; setToolTip and setContextMenu
were the gap. Mirror the existing lastX pattern:

- tray.mjs: dedupe setToolTip (exact string compare via lastTooltip) and
  setContextMenu (via lastMenuKey, a lightweight signature of menu-affecting
  fields: sessions/approvals/usage). menuKey is a string concat, cheaper than
  buildMenu itself, so skipping buildMenu when the key matches also saves
  work. Cache-after-call ordering matches lastTitle/lastTooltip so a throw
  forces a retry rather than skipping one. destroy() resets both new vars.
- useTraySync.ts: FLUSH_DEBOUNCE_MS 120 -> 500. Tray doesn't need sub-second
  updates; approvals are rare discrete events that flush through the debounce
  and the main app UI stays instant via SSE/stores.

The first change is the real fix; the second is a complement. Either alone
helps; together they eliminate the freeze under streaming.

packages/electron/tray.mjs

@@ -99,6 +99,8 @@ const toTemplateImage = (p) => {
 export const createTrayController = ({ idleIconPath, unseenIconPath, breathIconPaths, statusIconPaths, onAction }) => {
   let tray = null;
   let lastTitle = null;
+  let lastTooltip = null;
+  let lastMenuKey = null;
 
   // macOS auto-picks the @2x file next to each path and tints the alpha.
   // Windows uses the regular app icon and ignores template tinting.
@@ -274,6 +276,22 @@ export const createTrayController = ({ idleIconPath, unseenIconPath, breathIconP
     return Menu.buildFromTemplate(template);
   };
 
+  // Lightweight signature of the menu-affecting content — skips nativeImage
+  // and click handlers that can't be serialized. Cheaper than buildMenu itself.
+  const menuKey = (snapshot) => {
+    const sessions = Array.isArray(snapshot.sessions) ? snapshot.sessions : [];
+    const approvals = Array.isArray(snapshot.approvals) ? snapshot.approvals : [];
+    const usage = snapshot.usage && typeof snapshot.usage === 'object' ? snapshot.usage : {};
+    const groups = Array.isArray(usage.groups) ? usage.groups : [];
+    return JSON.stringify({
+      h: typeof snapshot.instanceName === 'string' ? snapshot.instanceName : '',
+      s: sessions.map((s) => `${s.id}|${s.title}|${s.status}|${s.unseen}|${s.hasError}|${s.subtitle}|${s.directory}`),
+      a: approvals.map((a) => `${a.id}|${a.kind}|${a.sessionId}|${a.sessionTitle}|${a.label}|${a.directory}`),
+      u: usage.mode || '',
+      g: groups.map((g) => `${g.provider}|${g.status}|${(Array.isArray(g.rows) ? g.rows : []).map((r) => `${r.label}|${r.value}`).join(',')}`),
+    });
+  };
+
   const update = (rawSnapshot) => {
     const snapshot = rawSnapshot && typeof rawSnapshot === 'object' ? rawSnapshot : {};
     const sessions = Array.isArray(snapshot.sessions) ? snapshot.sessions : [];
@@ -293,8 +311,16 @@ export const createTrayController = ({ idleIconPath, unseenIconPath, breathIconP
       lastTitle = title;
     }
     applyIconState(computeIconState(counts));
-    widget.setToolTip(computeTooltip(counts, sessions.length));
-    widget.setContextMenu(buildMenu(snapshot));
+    const tooltip = computeTooltip(counts, sessions.length);
+    if (tooltip !== lastTooltip) {
+      widget.setToolTip(tooltip);
+      lastTooltip = tooltip;
+    }
+    const key = menuKey(snapshot);
+    if (key !== lastMenuKey) {
+      widget.setContextMenu(buildMenu(snapshot));
+      lastMenuKey = key;
+    }
   };
 
   const destroy = () => {
@@ -304,6 +330,8 @@ export const createTrayController = ({ idleIconPath, unseenIconPath, breathIconP
     }
     tray = null;
     lastTitle = null;
+    lastTooltip = null;
+    lastMenuKey = null;
     iconState = null;
   };
 

packages/ui/src/hooks/useTraySync.ts

@@ -39,7 +39,7 @@ import type { QuestionRequest } from '@/types/question';
 const TRAY_ACTION_EVENT = 'openchamber:tray-action';
 // Event-driven updates do the real work; this is just a slow safety net.
 const POLL_INTERVAL_MS = 5000;
-const FLUSH_DEBOUNCE_MS = 120;
+const FLUSH_DEBOUNCE_MS = 500;
 // Pull the full cross-project session list periodically. SSE keeps the active
 // directory instant; this catches sessions created in directories this client
 // never opened (other worktrees, other projects, the TUI, …).
@@ -468,8 +468,8 @@ export const useTraySync = (): void => {
     };
 
     // Coalesce bursts (e.g. token-by-token streaming updates a store rapidly)
-    // into a single push, while staying near-instant for discrete events like
-    // a new session appearing.
+    // into at most one push per FLUSH_DEBOUNCE_MS; discrete events surface within
+    // that window. The main app UI stays instant via SSE/stores.
     const scheduleFlush = () => {
       if (disposed || flushTimer !== null) return;
       flushTimer = window.setTimeout(() => {