build: vendor the Slamtec rplidar SDK in third_party

The repo is now self-contained: driver_rplidar compiles the SDK from
third_party/rplidar_sdk (Linux sources only, teardown delete[] bug fixed
in place), so a plain cmake configure needs no SDK path and no probing —
the XLIDAR_RPLIDAR_SDK_DIR option and external references are gone.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plugins/driver_rplidar/CMakeLists.txt

@@ -1,35 +1,12 @@
-# The rplidar plugin compiles the vendor SDK straight into the plugin .so.
-# XLIDAR_RPLIDAR_SDK_DIR must point at a directory holding include/ + src/;
-# when unset, common local layouts are probed. Without an SDK the plugin is
-# skipped (the rest of the build is unaffected).
-
-if(NOT XLIDAR_RPLIDAR_SDK_DIR)
-    foreach(candidate
-            ${CMAKE_SOURCE_DIR}/third_party/rplidar_sdk
-            ${CMAKE_SOURCE_DIR}/../rplidar_sdk/sdk
-            ${CMAKE_SOURCE_DIR}/../xloc-monorepo/xlocd/deps/rplidar_sdk)
-        if(EXISTS ${candidate}/include/sl_lidar.h)
-            set(XLIDAR_RPLIDAR_SDK_DIR ${candidate})
-            break()
-        endif()
-    endforeach()
-endif()
-
-if(NOT XLIDAR_RPLIDAR_SDK_DIR OR NOT EXISTS ${XLIDAR_RPLIDAR_SDK_DIR}/include/sl_lidar.h)
-    message(WARNING "driver_rplidar: Slamtec SDK not found "
-                    "(set -DXLIDAR_RPLIDAR_SDK_DIR=...) — plugin skipped")
-    return()
-endif()
-
-message(STATUS "driver_rplidar: using SDK at ${XLIDAR_RPLIDAR_SDK_DIR}")
+# Compiles the vendored Slamtec SDK (third_party/rplidar_sdk) straight into
+# the plugin .so — no external dependency.
+set(RPLIDAR_SDK_DIR ${CMAKE_SOURCE_DIR}/third_party/rplidar_sdk)
 
 file(GLOB_RECURSE RPLIDAR_SDK_SOURCES CONFIGURE_DEPENDS
-    ${XLIDAR_RPLIDAR_SDK_DIR}/src/*.cpp)
-# The SDK ships win32/macOS arch files; keep Linux only.
-list(FILTER RPLIDAR_SDK_SOURCES EXCLUDE REGEX "arch/(win32|macOS)/")
+    ${RPLIDAR_SDK_DIR}/src/*.cpp)
 
 xlidar_add_plugin(driver_rplidar rplidar_driver.cpp ${RPLIDAR_SDK_SOURCES})
 target_include_directories(driver_rplidar SYSTEM PRIVATE
-    ${XLIDAR_RPLIDAR_SDK_DIR}/include
-    ${XLIDAR_RPLIDAR_SDK_DIR}/src
+    ${RPLIDAR_SDK_DIR}/include
+    ${RPLIDAR_SDK_DIR}/src
 )