fix(plugins): Python plugins see the host document again

Plugins read the host's document through a shared reference across the
dynamic-library boundary, and the entity index hashed with foldhash's
per-process seed, so every handle lookup from the plugin missed. The
codec now uses a fixed hasher (opencadcodec f385f75; kernel 9841749,
graph e9c23ad).

The Python IPC suite also caught up with intended changes: ATTDEF
renders its tag, DXF now keeps the lock-position flag, and the modify
audit turns associative arrays off since it checks loose copies.
The rate-limiter test waits for the host's check instead of a fixed
sleep that raced on macOS, and ENV_LOCK no longer cascades a poisoned
lock into every later test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ocs_plugin_api/src/ipc/v4/client.rs

@@ -1210,7 +1210,7 @@ mod tests {
 
     #[test]
     fn v4_client_notification_queue_size_env_is_honored() {
-        let _guard = ENV_LOCK.lock().unwrap();
+        let _guard = ENV_LOCK.lock().unwrap_or_else(|e| e.into_inner());
         let prev = std::env::var("OCS_PLUGIN_NOTIFY_QUEUE_SIZE").ok();
         std::env::set_var("OCS_PLUGIN_NOTIFY_QUEUE_SIZE", "7");
         assert_eq!(notify_queue_size(), 7);
@@ -1222,7 +1222,7 @@ mod tests {
 
     #[test]
     fn v4_client_notification_queue_drops_newest_on_overflow() {
-        let _guard = ENV_LOCK.lock().unwrap();
+        let _guard = ENV_LOCK.lock().unwrap_or_else(|e| e.into_inner());
         let prev = std::env::var("OCS_PLUGIN_NOTIFY_QUEUE_SIZE").ok();
         std::env::set_var("OCS_PLUGIN_NOTIFY_QUEUE_SIZE", "1");
         let (host_stream, mut runner_stream) = connect_pair();