refactor(render): move RenderBackend trait into op-editor-core

Cargo.lock

@@ -2278,6 +2278,7 @@ checksum = "9f7c3e4beb33f85d45ae3e3a1792185706c8e16d043238c593331cc7cd313b50"
 name = "op-editor-core"
 version = "0.1.0"
 dependencies = [
+ "glam",
  "jian-core",
  "jian-ops-schema",
 ]
@@ -2319,6 +2320,7 @@ dependencies = [
  "bitflags 2.11.1",
  "glam",
  "jian-core",
+ "op-editor-core",
  "op-i18n",
  "serde",
  "thiserror 1.0.69",

crates/op-editor-core/Cargo.toml

@@ -9,3 +9,7 @@ description = "OpenPencil editor state — selection/tool/history/viewport on ji
 [dependencies]
 jian-ops-schema = { path = "../../vendor/jian/crates/jian-ops-schema" }
 jian-core = { path = "../../vendor/jian/crates/jian-core" }
+
+# render_backend.rs uses glam::Vec2 as Point2D (spec §5.2). Pinned to the
+# same version openpencil-shell-core uses so both crates resolve one glam.
+glam = { version = "0.29", default-features = false, features = ["std"] }

crates/op-editor-core/src/lib.rs

@@ -1 +1,4 @@
 //! OpenPencil editor core.
+
+pub mod render_backend;
+pub use render_backend::*;

crates/openpencil-shell-core/Cargo.toml

@@ -36,6 +36,11 @@ jian-core = { path = "../../vendor/jian/crates/jian-core", version = "0.0.1" }
 # resolving `crate::i18n::*` / `crate::document::Locale` unchanged.
 op-i18n = { path = "../op-i18n" }
 
+# Phase 4 strangler reorg: the wasm-clean RenderBackend trait moved into
+# op-editor-core; shell-core re-exports it as `render_backend` so downstream
+# callers keep resolving `crate::render_backend::*` / `crate::RenderBackend`.
+op-editor-core = { path = "../op-editor-core" }
+
 [features]
 default = []
 serde = ["dep:serde"]

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

@@ -28,12 +28,15 @@ pub use op_i18n as i18n;
 pub mod jian;
 pub mod mcp;
 #[cfg(test)] mod mcp_tests;
-pub mod render_backend;
+// 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.
+pub use op_editor_core::render_backend;
 pub mod theme;
 pub mod widgets;
 
 // Re-export the primary API for upstream crates / widgets / tests.
-pub use render_backend::{Color, Point2D, Rect, RenderBackend, TextLayout};
+pub use op_editor_core::render_backend::{Color, Point2D, Rect, RenderBackend, TextLayout};
 pub use theme::Theme;
 
 /// Re-exports of Jian gesture / event types so shell consumers can use the