remove ocs_doc_api crate and DocApi v2 host integration

- Drop crates/ocs_doc_api from workspace and host dependency.
- Remove src/app/doc_api.rs and its module declaration.
- Strip DocApi v2 undo/dispatch plumbing from HostSession.
- Remove HostApi::doc_api_dispatch default method.
- Remove PluginRequest::DocApiRequest / PluginResponse::DocApiResponse.
- Revert plugin API version from 6 back to 5.

src/app/mod.rs

@@ -9,8 +9,6 @@ pub(crate) mod config;
 pub use automation::{export_headless, serve};
 mod command_driver;
 pub(crate) mod commands;
-#[cfg(not(target_arch = "wasm32"))]
-mod doc_api;
 mod document;
 pub(crate) mod expr_eval;
 mod find_replace;

src/app/plugin_host.rs

@@ -16,8 +16,6 @@ pub(crate) struct HostSession<'a> {
     app: &'a mut OpenCADStudio,
     tab: usize,
     doc_store: Option<DocumentSnapshotStore<DocumentViewData>>,
-    /// In-flight DocApi v2 undo delta (between `push_undo` and `finalize_op`).
-    doc_api_pending: Option<super::history::PendingDelta>,
 }
 
 impl<'a> HostSession<'a> {
@@ -26,7 +24,6 @@ impl<'a> HostSession<'a> {
             app,
             tab,
             doc_store: None,
-            doc_api_pending: None,
         }
     }
 
@@ -245,39 +242,6 @@ impl<'a> HostSession<'a> {
         self.app.push_undo_snapshot(self.tab, label);
     }
 
-    // ── DocApi v2 accessors (used by `app::doc_api` backend) ───────────────
-
-    pub(crate) fn scene(&self) -> &crate::scene::Scene {
-        &self.app.tabs[self.tab].scene
-    }
-
-    pub(crate) fn scene_mut(&mut self) -> &mut crate::scene::Scene {
-        &mut self.app.tabs[self.tab].scene
-    }
-
-    /// DocApi `push_undo`: capture entity and document-structure changes for one op.
-    pub(crate) fn begin_doc_api_undo(&mut self, label: &str) {
-        self.doc_api_pending = self.app.begin_undo(self.tab, label, 1, false);
-    }
-
-    pub(crate) fn cancel_doc_api_undo(&mut self) {
-        if self.doc_api_pending.take().is_some() {
-            self.scene_mut().take_undo_recording();
-        }
-    }
-
-    /// DocApi `finalize_op`: close the delta + republish the document view.
-    /// The underlying entity op (add/update/remove/register_solid_model) already
-    /// bumped `geometry_epoch`, so we do NOT bump again here — exactly one undo
-    /// step is recorded, and the epoch has advanced for this op.
-    pub(crate) fn commit_doc_api_undo(&mut self) {
-        self.set_dirty();
-        if let Some(pending) = self.doc_api_pending.take() {
-            self.app.commit_undo_delta(self.tab, pending);
-        }
-        self.publish_document_view();
-    }
-
     pub fn set_dirty(&mut self) {
         self.app.tabs[self.tab].dirty = true;
     }
@@ -396,10 +360,6 @@ impl HostApi for HostSession<'_> {
     fn close_document_view_v4(&mut self, tab_id: u64) {
         self.close_document_view_v4(tab_id)
     }
-    #[cfg(not(target_arch = "wasm32"))]
-    fn doc_api_dispatch(&mut self, tab_id: u64, bytes: &[u8]) -> Result<Vec<u8>, String> {
-        super::doc_api::execute_doc_api(self, tab_id, bytes)
-    }
 }
 
 /// Bridges a plugin's [`InteractiveCommand`](ocs_plugin_api::host::InteractiveCommand)