fix(notification): resolve platform in scheduler callbacks instead of using stale init value

The idle notification scheduler was initialized with platform 'unsupported'
before platform detection had run. This stale value was passed to send/playSound
callbacks, causing sendSessionNotification to silently no-op (no switch case for
'unsupported'). Session-idle notifications never fired as a result.

Fix: remove platform from scheduler options entirely. Callbacks now resolve
platform via ensureNotificationPlatform() which is sync, cached, and already
called by each event handler before scheduling.

src/hooks/session-notification-scheduler.ts

@@ -1,5 +1,4 @@
 import type { PluginInput } from "@opencode-ai/plugin"
-import type { Platform } from "./session-notification-sender"
 
 type SessionNotificationConfig = {
   playSound: boolean
@@ -13,11 +12,10 @@ type SessionNotificationConfig = {
 
 export function createIdleNotificationScheduler(options: {
   ctx: PluginInput
-  platform: Platform
   config: SessionNotificationConfig
   hasIncompleteTodos: (ctx: PluginInput, sessionID: string) => Promise<boolean>
-  send: (ctx: PluginInput, platform: Platform, sessionID: string) => Promise<void>
-  playSound: (ctx: PluginInput, platform: Platform, soundPath: string) => Promise<void>
+  send: (ctx: PluginInput, sessionID: string) => Promise<void>
+  playSound: (ctx: PluginInput, soundPath: string) => Promise<void>
 }) {
   const notifiedSessions = new Set<string>()
   const pendingTimers = new Map<string, ReturnType<typeof setTimeout>>()
@@ -136,10 +134,10 @@ export function createIdleNotificationScheduler(options: {
 
       notifiedSessions.add(sessionID)
 
-      await options.send(options.ctx, options.platform, sessionID)
+      await options.send(options.ctx, sessionID)
 
       if (options.config.playSound && options.config.soundPath) {
-        await options.playSound(options.ctx, options.platform, options.config.soundPath)
+        await options.playSound(options.ctx, options.config.soundPath)
       }
     } finally {
       executingNotifications.delete(sessionID)

src/hooks/session-notification.ts

@@ -47,10 +47,10 @@ export function createSessionNotification(ctx: PluginInput, config: SessionNotif
 
   const scheduler = createIdleNotificationScheduler({
     ctx,
-    platform: "unsupported",
     config: mergedConfig,
     hasIncompleteTodos,
-    send: async (hookCtx, platform, sessionID) => {
+    send: async (hookCtx, sessionID) => {
+      const platform = ensureNotificationPlatform()
       if (typeof hookCtx.client.session.get !== "function" && typeof hookCtx.client.session.messages !== "function") {
         await sessionNotificationSender.sendSessionNotification(hookCtx, platform, mergedConfig.title, mergedConfig.message)
         return
@@ -64,7 +64,10 @@ export function createSessionNotification(ctx: PluginInput, config: SessionNotif
 
       await sessionNotificationSender.sendSessionNotification(hookCtx, platform, content.title, content.message)
     },
-    playSound: sessionNotificationSender.playSessionNotificationSound,
+    playSound: async (hookCtx, soundPath) => {
+      const platform = ensureNotificationPlatform()
+      await sessionNotificationSender.playSessionNotificationSound(hookCtx, platform, soundPath)
+    },
   })
 
   const QUESTION_TOOLS = new Set(["question", "ask_user_question", "askuserquestion"])