fix(session-notification): revert PR #543 and add proper notification plugin conflict detection (#575)

* revert: undo PR #543 changes (bun shell GC crash was misdiagnosed)

This reverts commit 4a38e70 (PR #543) and 2064568 (follow-up fix).

## Why This Revert

The original diagnosis was incorrect. PR #543 assumed Bun's
ShellInterpreter GC bug was causing Windows crashes, but further
investigation revealed the actual root cause:

**The crash occurs when oh-my-opencode's session-notification runs
alongside external notification plugins (e.g., @mohak34/opencode-notifier).**

Evidence:
- User removed opencode-notifier plugin → crashes stopped
- Release version (with original ctx.$ code) works fine when used alone
- No widespread crash reports from users without external notifiers
- Both plugins listen to session.idle and send concurrent notifications

The real issue is a conflict between two notification systems:
1. oh-my-opencode: ctx.$ → PowerShell → Windows.UI.Notifications
2. opencode-notifier: node-notifier → SnoreToast.exe

A proper fix will detect and handle this conflict gracefully.

Refs: #543, oven-sh/bun#23177, oven-sh/bun#24368
See: docs/CRASH_INVESTIGATION_TIMELINE.md (in follow-up commit)

* fix(session-notification): detect and avoid conflict with external notification plugins

When oh-my-opencode's session-notification runs alongside external
notification plugins like opencode-notifier, both listen to session.idle
and send concurrent notifications. This can cause crashes on Windows
due to resource contention between different notification mechanisms:
- oh-my-opencode: ctx.$ → PowerShell → Windows.UI.Notifications
- opencode-notifier: node-notifier → SnoreToast.exe

This commit adds:
1. External plugin detection (checks opencode.json for known notifiers)
2. Auto-disable of session-notification when conflict detected
3. Console warning explaining the situation
4. Config option 'notification.force_enable' to override

Known notification plugins detected:
- opencode-notifier
- @mohak34/opencode-notifier
- mohak34/opencode-notifier

This is the actual fix for the Windows crash issue previously
misdiagnosed as a Bun.spawn GC bug (PR #543).

Refs: #543

* docs: add crash investigation timeline explaining the real root cause

Documents the investigation journey from initial misdiagnosis (Bun GC bug)
to discovering the actual root cause (notification plugin conflict).

Key findings:
- PR #543 was based on incorrect assumption
- The real issue is concurrent notification plugins
- oh-my-opencode + opencode-notifier = crash on Windows
- Either plugin alone works fine

* fix: address review feedback - add PowerShell escaping and use existing JSONC parser

- Add back single-quote escaping for PowerShell soundPath to prevent command failures
- Replace custom stripJsonComments with existing parseJsoncSafe from jsonc-parser
- All 655 tests pass

---------

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/hooks/session-notification.test.ts

@@ -1,6 +1,4 @@
-import { describe, expect, test, beforeEach, afterEach, spyOn, mock } from "bun:test"
-import { EventEmitter } from "node:events"
-import * as childProcess from "node:child_process"
+import { describe, expect, test, beforeEach, afterEach, spyOn } from "bun:test"
 
 import { createSessionNotification } from "./session-notification"
 import { setMainSession, subagentSessions } from "../features/claude-code-session-state"
@@ -8,11 +6,20 @@ import * as utils from "./session-notification-utils"
 
 describe("session-notification", () => {
   let notificationCalls: string[]
-  let spawnMock: ReturnType<typeof spyOn>
 
   function createMockPluginInput() {
     return {
-      $: async () => ({ stdout: "", stderr: "", exitCode: 0 }),
+      $: async (cmd: TemplateStringsArray | string, ...values: any[]) => {
+        // #given - track notification commands (osascript, notify-send, powershell)
+        const cmdStr = typeof cmd === "string" 
+          ? cmd 
+          : cmd.reduce((acc, part, i) => acc + part + (values[i] ?? ""), "")
+        
+        if (cmdStr.includes("osascript") || cmdStr.includes("notify-send") || cmdStr.includes("powershell")) {
+          notificationCalls.push(cmdStr)
+        }
+        return { stdout: "", stderr: "", exitCode: 0 }
+      },
       client: {
         session: {
           todo: async () => ({ data: [] }),
@@ -25,18 +32,6 @@ describe("session-notification", () => {
   beforeEach(() => {
     notificationCalls = []
     
-    // Mock spawn to track notification commands
-    // Uses node:child_process.spawn instead of Bun shell to avoid GC crash
-    spawnMock = spyOn(childProcess, "spawn").mockImplementation(((cmd: string, args?: string[]) => {
-      // Track notification commands (osascript, notify-send, powershell)
-      if (cmd.includes("osascript") || cmd.includes("notify-send") || cmd.includes("powershell")) {
-        notificationCalls.push(`${cmd} ${(args ?? []).join(" ")}`)
-      }
-      const emitter = new EventEmitter()
-      setTimeout(() => emitter.emit("close", 0), 0)
-      return emitter as any
-    }) as typeof childProcess.spawn)
-    
     spyOn(utils, "getOsascriptPath").mockResolvedValue("/usr/bin/osascript")
     spyOn(utils, "getNotifySendPath").mockResolvedValue("/usr/bin/notify-send")
     spyOn(utils, "getPowershellPath").mockResolvedValue("powershell")