fix(core): also register global shutdown hook in PackageManager(Impl&) constructor

Manager::Manager() bypasses PackageManager() default constructor and
calls PackageManager(Impl&) directly. The default constructor registered
a global shutdown hook (setGlobalShutdownHook) to release ObjectPool
references before plugin DLLs are unloaded, but the Impl& constructor
path was missing this registration.

Without this hook, if the Runtime destruction callback (registered by
setupG2pOnnxDriver) does not fire (e.g. multiple Runtime instances,
Runtime not destroyed before static Manager destruction), the Manager
singleton's destructor at process exit triggers cleanup of Task objects
whose vtables reside in already-unloaded plugin DLLs, causing a
use-after-free crash in shared_ptr::_Decref.

This completes the fix chain:
  - 3d1d66e (weak_ptr in factory)
  - 5772823 (destruction callback)
  - b4e2806 (global hook in default constructor)
  - This commit (global hook in Impl& constructor)

Author: wolfgitpr

lib/G2P/Core/PackageManager.cpp

@@ -617,6 +617,28 @@ namespace srt::g2p {
     // ============================================================================
 
     PackageManager::PackageManager(Impl &impl) : _impl(&impl) {
+        // Register a process-wide shutdown hook so that when ANY Runtime
+        // instance destructs (before plugin DLLs are unloaded), this
+        // PackageManager's ObjectPool references are released while the
+        // plugin DLLs are still loaded.
+        //
+        // This is necessary because Manager (a subclass that uses this
+        // constructor path) is a static singleton whose destructor runs
+        // AFTER the host's Runtime. Without this hook, the Manager
+        // destructor would release Task/SessionFactory shared_ptrs whose
+        // vtables reside in already-unloaded plugin DLLs, causing
+        // use-after-free crashes in shared_ptr::_Decref.
+        //
+        // The hook captures `this` (raw pointer to the static singleton,
+        // whose address is stable for the process lifetime). shutdown() is
+        // idempotent, so a later destructor call is a no-op.
+        //
+        // NOTE: This is identical to the hook registration in the default
+        // constructor; both paths must register it since Manager bypasses
+        // the default constructor.
+        srt::core::Runtime::setGlobalShutdownHook([this]() {
+            _impl->shutdown();
+        });
     }
 
     PackageManager::PackageManager() : srt::core::PluginFactory(), _impl(new Impl(this)) {