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/index.ts

@@ -62,7 +62,7 @@ import {
 import { BackgroundManager } from "./features/background-agent";
 import { SkillMcpManager } from "./features/skill-mcp-manager";
 import { type HookName } from "./config";
-import { log } from "./shared";
+import { log, detectExternalNotificationPlugin, getNotificationConflictWarning } from "./shared";
 import { loadPluginConfig } from "./plugin-config";
 import { createModelCacheState, getModelLimit } from "./plugin-state";
 import { createConfigHandler } from "./plugin-handlers";
@@ -83,9 +83,24 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
   const sessionRecovery = isHookEnabled("session-recovery")
     ? createSessionRecoveryHook(ctx, { experimental: pluginConfig.experimental })
     : null;
-  const sessionNotification = isHookEnabled("session-notification")
-    ? createSessionNotification(ctx)
-    : null;
+  
+  // Check for conflicting notification plugins before creating session-notification
+  let sessionNotification = null;
+  if (isHookEnabled("session-notification")) {
+    const forceEnable = pluginConfig.notification?.force_enable ?? false;
+    const externalNotifier = detectExternalNotificationPlugin(ctx.directory);
+    
+    if (externalNotifier.detected && !forceEnable) {
+      // External notification plugin detected - skip our notification to avoid conflicts
+      console.warn(getNotificationConflictWarning(externalNotifier.pluginName!));
+      log("session-notification disabled due to external notifier conflict", {
+        detected: externalNotifier.pluginName,
+        allPlugins: externalNotifier.allPlugins,
+      });
+    } else {
+      sessionNotification = createSessionNotification(ctx);
+    }
+  }
 
   const commentChecker = isHookEnabled("comment-checker")
     ? createCommentCheckerHooks(pluginConfig.comment_checker)