fix(plugins): preserve document path encoding

Keep OS-native path data intact across IPC instead of replacing non-UTF-8 bytes.

Refs #901

crates/ocs_plugin_api/src/host.rs

@@ -542,9 +542,8 @@ pub trait HostApi {
     }
 
     /// Return the filesystem path of the document in tab `tab_id`, if any.
-    /// Added after API v4; appended at the very end so older plugins compiled
-    /// without it keep stable vtable indices. The default returns `None`;
-    /// in-process hosts should override it to expose the real path.
+    /// Added in API v5. The default returns `None`; in-process hosts should
+    /// override it to expose the real path.
     fn document_path(&self, tab_id: u64) -> Option<PathBuf> {
         let _ = tab_id;
         None

crates/ocs_plugin_api/src/ipc/protocol.rs

@@ -136,7 +136,7 @@ pub enum PluginRequest {
     CloseDocumentViewV4 { tab_id: u64 },
     /// V4: ask the host for the stable tab identifier of the active tab.
     GetTabId,
-    /// V4: ask the host for the filesystem path of the document in `tab_id`.
+    /// V5: ask the host for the filesystem path of the document in `tab_id`.
     DocumentPath { tab_id: u64 },
 }
 
@@ -162,8 +162,8 @@ pub enum PluginResponse {
     },
     /// V4: stable tab identifier of the active tab.
     TabId(u64),
-    /// V4: filesystem path of the document in the requested tab, if any.
-    DocumentPath(Option<String>),
+    /// V5: filesystem path of the document in the requested tab, if any.
+    DocumentPath(Option<std::ffi::OsString>),
 }
 
 /// Messages sent from the host to the plugin runner.

crates/ocs_plugin_api/src/ipc/server.rs

@@ -74,8 +74,8 @@ pub fn handle_plugin_request(
             PluginResponse::Ok
         }
         GetTabId => PluginResponse::TabId(host.tab_id()),
-        DocumentPath { tab_id } => {
-            PluginResponse::DocumentPath(host.document_path(tab_id).map(|p| p.to_string_lossy().to_string()))
-        }
+        DocumentPath { tab_id } => PluginResponse::DocumentPath(
+            host.document_path(tab_id).map(|path| path.into_os_string()),
+        ),
     }
 }