fix: resolve plugins that are missing locally (physical file deleted) (#14861)

* fix: resolve plugins that are missing locally (physical file deleted)

* fix: don't treat file not found as an error

src/slic3r/plugin/PluginManager.hpp

@@ -132,6 +132,11 @@ public:
     bool try_get_plugin_descriptor(const std::string& plugin_key, PluginDescriptor& out) const;
     // Same, but only for packages that are loadable (i.e. not an invalid package).
     bool try_get_valid_plugin_descriptor(const std::string& plugin_key, PluginDescriptor& out) const;
+    // Packages that were present in the previous discovery pass but were not found on disk in the
+    // latest rescan. They are retained until the user explicitly removes them or a later scan finds
+    // them again.
+    std::vector<PluginDescriptor> get_missing_plugin_descriptors() const;
+    void remove_missing_plugins(const std::vector<std::string>& plugin_keys);
     // Packages whose .install_state.json marks them for auto-load.
     std::vector<std::string> get_enabled_plugin_keys() const;
     // The package owning a loaded capability, for the by-name dispatch path.
@@ -262,6 +267,7 @@ private:
 
     // Every discovered plugin, loaded or not. module == nullptr => not loaded.
     std::vector<Plugin> m_plugins;
+    std::unordered_set<std::string> m_missing_plugin_keys;
 
     std::unordered_set<std::string> m_load_in_progress;
     // Keys whose in-flight load has been cancelled. Cancellation does NOT remove the key from