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.

crates/ocs_plugin_api/build.rs

@@ -908,7 +908,7 @@ fn generate_version_info(out_dir: &Path) {
         "acadrust_version": acadrust.version.to_string(),
         "acadrust_source": acadrust.source.as_ref().map(|s| s.to_string()),
         "rustc_version": rustc_version,
-        "api_version": 6,
+        "api_version": 5,
         "api_version_min_supported": 2,
         "build_timestamp": build_timestamp,
     });

crates/ocs_plugin_api/src/host.rs

@@ -552,18 +552,6 @@ pub trait HostApi {
         let _ = tab_id;
         None
     }
-
-    /// DocApi v2 (`ocs_doc_api`): dispatch one bincode-serialized `DocApiEnvelope`
-    /// (one write op OR a read-only query batch) and return the bincode-serialized
-    /// `Result<Receipt, ApiError>`. Opaque bytes:
-    /// this crate does not depend on `ocs_doc_api`, it only routes the envelope.
-    ///
-    /// Added for the DocApi v2 adapter. The default returns `Err` ("not supported");
-    /// the in-process host (`HostSession`) overrides it to call the DocApi executor.
-    fn doc_api_dispatch(&mut self, tab_id: u64, bytes: &[u8]) -> Result<Vec<u8>, String> {
-        let _ = (tab_id, bytes);
-        Err("DocApi v2 not supported by this host".to_string())
-    }
 }
 
 /// Simplified, read-only entity kind exposed by [`DocumentReader`].

crates/ocs_plugin_api/src/ipc/protocol.rs

@@ -138,12 +138,6 @@ pub enum PluginRequest {
     GetTabId,
     /// V5: ask the host for the filesystem path of the document in `tab_id`.
     DocumentPath { tab_id: u64 },
-    /// DocApi v2 (`ocs_doc_api`): carry one bincode-serialized `DocApiEnvelope`
-    /// (one write op OR a read-only query batch). Appended at the end to keep
-    /// existing discriminants stable. The host routes this to the DocApi executor.
-    /// `serde_bytes` keeps the payload a single length-prefixed bulk copy (the
-    /// outer frame would otherwise walk it byte-by-byte).
-    DocApiRequest { tab_id: u64, #[serde(with = "serde_bytes")] bytes: Vec<u8> },
 }
 
 /// Responses the host sends back for `PluginRequest`.
@@ -170,10 +164,6 @@ pub enum PluginResponse {
     TabId(u64),
     /// V5: filesystem path of the document in the requested tab, if any.
     DocumentPath(Option<std::ffi::OsString>),
-    /// DocApi v2 (`ocs_doc_api`): the bincode-serialized `Result<Receipt, ApiError>` answering a
-    /// `PluginRequest::DocApiRequest`. Appended at the end (discriminant stability).
-    /// `serde_bytes` keeps the payload a single length-prefixed bulk copy.
-    DocApiResponse { #[serde(with = "serde_bytes")] bytes: Vec<u8> },
 }
 
 /// Messages sent from the host to the plugin runner.

crates/ocs_plugin_api/src/ipc/server.rs

@@ -77,9 +77,5 @@ pub fn handle_plugin_request(
         DocumentPath { tab_id } => PluginResponse::DocumentPath(
             host.document_path(tab_id).map(|path| path.into_os_string()),
         ),
-        DocApiRequest { tab_id, bytes } => match host.doc_api_dispatch(tab_id, &bytes) {
-            Ok(bytes) => PluginResponse::DocApiResponse { bytes },
-            Err(msg) => PluginResponse::Error(msg),
-        },
     }
 }

crates/ocs_plugin_api/src/manifest.rs

@@ -18,15 +18,9 @@
 /// plugins and appends `document_reader` / `document_view` at the end of the
 /// vtable so API v2 plugins keep working. v4 adds full-duplex notifications on
 /// a multiplexed socket while leaving the V2/V3 ABI and protocol untouched. v5
-/// adds the `BuiltinPlugin::on_load` lifecycle callback.
-/// Host ABI major version. Bumped to 6 when the DocApi v2 surface
-/// (`PluginRequest::DocApiRequest` / `PluginResponse::DocApiResponse` +
-/// `HostApi::doc_api_dispatch`) was added: plugins that call DocApi require an
-/// API-6 host and are rejected at handshake by older (API ≤ 5) hosts, instead of
-/// failing at runtime with a bincode-decode transport error. The DocApi wire
-/// changes are append-only and `doc_api_dispatch` is a defaulted method, so
-/// older V2–V5 plugins still load unchanged on an API-6 host.
-pub const API_VERSION: u32 = 6;
+/// adds the `BuiltinPlugin::on_load` lifecycle callback and
+/// `HostApi::document_path`.
+pub const API_VERSION: u32 = 5;
 
 /// Oldest plugin API major the current host still loads. This keeps previously
 /// compiled cdylibs usable as long as their vtable layout is a prefix of the