Fix build dependency ordering for cppbind.ts

Resolves issue #21434 where Bun fails to build the first time because
it tries to generate C++ → Zig bindings before installing @lezer/cpp.

The cppbind.ts script imports @lezer/cpp, but the CMake build system
was running this script before ensuring that the root-level node_modules
was installed.

Changes:
- Add register_bun_install() call for root directory in BuildBun.cmake
- Make bun-cppbind target depend on root node_modules installation
- This ensures @lezer/cpp is available before cppbind.ts runs

🤖 Generated with [Claude Code](https://claude.ai/code)

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

cmake/targets/BuildBun.cmake

@@ -316,6 +316,14 @@ set(BUN_CPP_OUTPUTS
   ${CODEGEN_PATH}/cpp.zig
 )
 
+# Root-level node_modules install needed for @lezer/cpp dependency used by cppbind.ts
+register_bun_install(
+  CWD
+    ${CWD}
+  NODE_MODULES_VARIABLE
+    BUN_ROOT_NODE_MODULES
+)
+
 register_command(
   TARGET
     bun-cppbind
@@ -329,6 +337,7 @@ register_command(
   SOURCES
     ${BUN_JAVASCRIPT_CODEGEN_SOURCES}
     ${BUN_CXX_SOURCES}
+    ${BUN_ROOT_NODE_MODULES}
   OUTPUTS
     ${BUN_CPP_OUTPUTS}
 )