refactor: extract op-mcp crate

Relocate mcp.rs + mcp/* + mcp_tests.rs out of openpencil-shell-core
into a dedicated op-mcp crate. The MCP tool registry + JSON-RPC stdio
layer only depends on jian-ops-schema + op-editor-core (its tools
build on EditorState / EditorCommand). mcp.rs becomes the crate's
lib.rs; the mcp/ submodule files flatten to src/ so the `pub mod`
declarations resolve unchanged, and intra-module `super::` paths stay
valid. mcp_tests.rs becomes a #[cfg(test)] mod of lib.rs with its
`super::mcp::` paths rewritten to `crate::`. openpencil-desktop's
mcp_serve.rs now imports `op_mcp::*`. Pure relocation, no behaviour
change; 138 tests move with their code.

crates/op-mcp/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "op-mcp"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+description = "OpenPencil MCP server — JSON-RPC tool registry over op-editor-core EditorState / EditorCommand"
+
+[lib]
+name = "op_mcp"
+path = "src/lib.rs"
+
+[dependencies]
+jian-ops-schema = { path = "../../vendor/jian/crates/jian-ops-schema" }
+op-editor-core = { path = "../op-editor-core" }

crates/op-mcp/src/lib.rs

@@ -8,10 +8,7 @@
 //! `op_editor_core::EditorState` / `op_editor_core::EditorCommand`.
 //! Read tools now snapshot an `EditorState` (canonical `PenDocument`);
 //! write tools emit an `op_editor_core::EditorCommand` the host applies
-//! via `EditorState::apply`. The module physically still lives inside
-//! `openpencil-shell-core` — an `op-mcp` crate extraction is a later
-//! Phase-7 task. shell-core's own `Document` (used by the widgets) is
-//! untouched.
+//! via `EditorState::apply`.
 //!
 //! ## Component-command gap
 //!
@@ -47,6 +44,9 @@ pub mod selected_ops_tools;
 #[cfg(test)] mod replace_node_tests;
 #[cfg(test)] mod batch_design_tests;
 #[cfg(test)] mod scalar_vars_tests;
+// Cross-cutting tests for the crate spine — stdio dispatch + parser
+// invariants + a few read-tool registry round-trips.
+#[cfg(test)] mod mcp_tests;
 
 // The MCP command DTO is now `op_editor_core::EditorCommand` — the
 // faithful port of the old shell-core `McpCommand`. Re-exported here

crates/op-mcp/src/mcp_tests.rs

@@ -4,8 +4,8 @@
 //! Ported off the old shell-core `Document` onto `op_editor_core::
 //! EditorState`.
 
-use super::mcp::test_fixtures::{add_variable, sample, state_with};
-use super::mcp::*;
+use crate::test_fixtures::{add_variable, sample, state_with};
+use crate::*;
 use jian_ops_schema::variable::{VariableKind, VariableScalar};
 use std::collections::BTreeMap;
 
@@ -280,10 +280,10 @@ fn json_escape_handles_special_chars() {
 
 #[test]
 fn get_document_info_reports_snapshot_via_registry() {
-    use super::mcp::test_fixtures::frame;
+    use crate::test_fixtures::frame;
     let f = frame("n10", "F", 0.0, 0.0, 200.0, 100.0, vec![
-        super::mcp::test_fixtures::rect("n11", "a", 0.0, 0.0, 10.0, 10.0),
-        super::mcp::test_fixtures::rect("n12", "b", 20.0, 0.0, 10.0, 10.0),
+        crate::test_fixtures::rect("n11", "a", 0.0, 0.0, 10.0, 10.0),
+        crate::test_fixtures::rect("n12", "b", 20.0, 0.0, 10.0, 10.0),
     ]);
     let s = state_with(vec![f]);
     let info = document_info_snapshot(&s);

crates/op-mcp/src/replace_node_tests.rs

@@ -179,7 +179,7 @@ fn replace_node_rejects_malformed_drop_children() {
 
 #[test]
 fn parser_refuses_structured_drop_children_at_wire_layer() {
-    use crate::mcp::parse_tool_call;
+    use crate::parse_tool_call;
     for bad_json in [
         r#"{"id":1,"method":"replace_node","params":{"node_id":"n10","kind":"rect","name":"X","x":"0","y":"0","width":"5","height":"5","drop_children":{}}}"#,
         r#"{"id":1,"method":"replace_node","params":{"node_id":"n10","kind":"rect","name":"X","x":"0","y":"0","width":"5","height":"5","drop_children":[true]}}"#,

crates/openpencil-desktop/Cargo.toml

@@ -21,6 +21,10 @@ openpencil-shell-native = { path = "../openpencil-shell-native", version = "0.1.
 # `op_editor_core::EditorState` (canonical `.op` document) instead of the
 # old shell-core `Document`.
 op-editor-core = { path = "../op-editor-core" }
+# Phase 7 strangler reorg: the MCP tool registry + JSON-RPC stdio layer
+# (`mcp.rs` + `mcp/*`) was extracted out of openpencil-shell-core into the
+# op-mcp crate; `mcp_serve.rs` registers tools through `op_mcp::*`.
+op-mcp = { path = "../op-mcp" }
 # Canonical `.op` (PenDocument) → shell `Document` loader / adapter.
 # Extracted out of this binary into a shared library crate so library
 # crates (openpencil-shell-native) can reuse the conversion;

crates/openpencil-desktop/src/mcp_serve.rs

@@ -29,7 +29,7 @@ use std::io::{BufRead, BufReader, BufWriter, Write};
 use std::path::PathBuf;
 
 use op_editor_core::EditorState;
-use openpencil_shell_core::mcp::{
+use op_mcp::{
     batch_design_snapshot, copy_node_snapshot, delete_node_snapshot,
     design_content_snapshot, design_refine_snapshot, design_skeleton_snapshot,
     add_page_snapshot, clear_selection_snapshot, create_component_snapshot,

crates/openpencil-shell-core/src/lib.rs

@@ -30,11 +30,9 @@ pub mod layout_scene;
 // Canvas hit-test (input path) over `LayoutScene` — replaces the
 // `&Document`-bound `node_at_doc_point` / `nodes_intersecting_doc_rect`.
 pub mod layout_scene_hit;
-pub mod mcp;
 // Paint-time design-variable aggregation consumed by the
 // `LayoutScene` scene builder (`$ref` fill / stroke resolution).
 pub mod scene_vars;
-#[cfg(test)] mod mcp_tests;
 // Phase 4 strangler reorg: the wasm-clean RenderBackend trait moved into the
 // op-editor-core crate. Re-exported as `render_backend` so `crate::render_backend::*`
 // paths still resolve.