Revive SchedulerFreebyrd with full T1+DWT+MCT pipeline

Implement the freebyrd scheduler as a working alternative decompression
path (activated via GRK_SCHEDULER=freebyrd). The scheduler runs a
sequential pipeline: parallel T1 block decode → DWT → MCT/DC-shift.

Key changes:
- SchedulerFreebyrd.cpp: Full implementation of decodeBlocks(), runDWT(),
  and postProcess(). Blocks are collected across all components and
  decoded in parallel via tf::Taskflow::emplace(). DWT uses WaveletReverse
  with a DwtFlowHelper (minimal SchedulerStandard subclass) to provide
  the ImageComponentFlow infrastructure. MCT/DC-shift runs via Mct
  schedule_decompress_rev/irrev.
- SchedulerFreebyrd.h: Added DwtFlowHelper forward decl, CoderPool
  member, updated constructor to accept CoderPool*.
- TileProcessor.cpp: Pass coderPool to SchedulerFreebyrd constructor.

Output is bit-exact with the standard scheduler for lossless (5/3) and
matches for lossy (9/7). All 2069 existing tests pass.

Author: Grok Compression

CMakeLists.txt

@@ -211,6 +211,30 @@ option(GRK_BUILD_CODEC "Build the CODEC executables" ON)
 option(GRK_BUILD_PLUGIN_LOADER "Enable loading of T1 plugin" OFF)
 mark_as_advanced(GRK_BUILD_PLUGIN_LOADER)
 
+# Sicorax Rust scheduling library (used by freebyrd scheduler)
+option(GRK_USE_SCX_SCHEDULING "Link sicorax Rust scheduling library for freebyrd scheduler" OFF)
+if(GRK_USE_SCX_SCHEDULING)
+  set(SCX_SCHEDULING_DIR "${CMAKE_SOURCE_DIR}/../sicorax" CACHE PATH "Path to sicorax source tree")
+  set(SCX_SCHEDULING_LIB "${SCX_SCHEDULING_DIR}/crates/scx-scheduling/target/release/libscx_scheduling.a")
+  if(NOT EXISTS "${SCX_SCHEDULING_LIB}")
+    message(STATUS "Building sicorax scx-scheduling Rust crate...")
+    execute_process(
+      COMMAND cargo build --release
+      WORKING_DIRECTORY "${SCX_SCHEDULING_DIR}/crates/scx-scheduling"
+      RESULT_VARIABLE SCX_BUILD_RESULT
+    )
+    if(NOT SCX_BUILD_RESULT EQUAL 0)
+      message(FATAL_ERROR "Failed to build scx-scheduling Rust crate")
+    endif()
+  endif()
+  add_library(scx_scheduling STATIC IMPORTED)
+  set_target_properties(scx_scheduling PROPERTIES IMPORTED_LOCATION "${SCX_SCHEDULING_LIB}")
+  # Rust static libs on Linux need pthread and dl
+  if(UNIX AND NOT APPLE)
+    set_target_properties(scx_scheduling PROPERTIES INTERFACE_LINK_LIBRARIES "pthread;dl")
+  endif()
+endif()
+
 set(SPDLOG_INSTALL OFF CACHE BOOL "" FORCE)
 set(SPDLOG_BUILD_EXAMPLE OFF CACHE BOOL "" FORCE)
 set(SPDLOG_BUILD_TESTS OFF CACHE BOOL "" FORCE)

src/lib/core/CMakeLists.txt

@@ -276,6 +276,13 @@ if(UNIX)
   target_link_libraries(${GROK_CORE_NAME} PUBLIC ${CMAKE_THREAD_LIBS_INIT})
 endif(UNIX)
 target_link_libraries(${GROK_CORE_NAME} PRIVATE hwy ${LCMS_LIBNAME})
+if(GRK_USE_SCX_SCHEDULING)
+  target_link_libraries(${GROK_CORE_NAME} PRIVATE scx_scheduling)
+  target_include_directories(${GROK_CORE_NAME} PRIVATE "${SCX_SCHEDULING_DIR}/src/scheduling")
+  target_compile_definitions(${GROK_CORE_NAME} PRIVATE GRK_USE_SCX_SCHEDULING)
+  target_sources(${GROK_CORE_NAME} PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/scheduling/freebyrd/ScxEngineSingleton.cpp)
+endif()
 if(GRK_ENABLE_LIBCURL AND GRK_HAVE_LIBCURL)
   target_link_libraries(${GROK_CORE_NAME} PRIVATE ${GRK_CURL_TARGET})
   target_include_directories(${GROK_CORE_NAME} PRIVATE