feat(plugins): expose document path to plugins via HostApi

OpenCADStudio/plugins#901 (comment)

- Add HostApi::document_path(tab_id) returning Option<PathBuf>.
- Add PluginRequest::DocumentPath and PluginResponse::DocumentPath for
  out-of-process plugins.
- Implement the request in the IPC server and in both V3/V4 plugin-side
  HostApi proxies.
- Implement HostSession::document_path by looking up the tab by id and
  returning its current_path.

src/app/plugin_host.rs

@@ -35,6 +35,14 @@ impl<'a> HostSession<'a> {
         self.app.tabs[self.tab].id
     }
 
+    pub fn document_path(&self, tab_id: u64) -> Option<std::path::PathBuf> {
+        self.app
+            .tabs
+            .iter()
+            .find(|t| t.id == tab_id)
+            .and_then(|t| t.current_path.clone())
+    }
+
     #[cfg(not(target_arch = "wasm32"))]
     pub fn document_view_v4(&mut self, tab_id: u64) -> Option<ocs_plugin_api::shm::DocumentViewInfo> {
         if tab_id != self.tab_id() {
@@ -341,6 +349,9 @@ impl HostApi for HostSession<'_> {
     fn tab_id(&self) -> u64 {
         self.tab_id()
     }
+    fn document_path(&self, tab_id: u64) -> Option<std::path::PathBuf> {
+        self.document_path(tab_id)
+    }
     #[cfg(not(target_arch = "wasm32"))]
     fn document_view_v4(&mut self, tab_id: u64) -> Option<ocs_plugin_api::shm::DocumentViewInfo> {
         self.document_view_v4(tab_id)