Refactor: extract AICPU scheduler into SchedulerContext class (a2a3 + a5)

[poursoul]

Summary

Extract the AICPU scheduler logic from aicpu_executor.cpp into a dedicated runtime/scheduler/ subdirectory with a new SchedulerContext class. Applied consistently to both a2a3 and a5 architectures.

• Extract SchedulerContext class: split completion, cold-path, and dispatch methods out of AicpuExecutor into separate .cpp files, shrinking aicpu_executor.cpp from ~2800 lines to ~1200–1500 lines
• Create runtime/scheduler/ directory: houses scheduler_types.h (type definitions & constants), scheduler_context.h (class declaration), scheduler_completion.cpp, scheduler_cold_path.cpp, scheduler_dispatch.cpp, plus relocated pto_scheduler.h/.cpp
• Create runtime/shared/ directory: isolate host build dependencies to only runtime.cpp and pto_shared_memory.cpp, preventing device-only code from compiling into the host .so
• Integrate PMU profiling: adapt upstream PMU sampling (Support: add a2a3 PMU profiling path #639) into SchedulerContext (per-task recording, init, buffer flush)
• Sync documentation: update function names and file path references in device_log_profiling.md, profiling_levels.md, tensor-dump.md, and dynamic-linking.md

Pure structural refactoring — no behavioral change.

Changes

Area	Change
src/{a2a3,a5}/.../runtime/scheduler/	New SchedulerContext class with 5 header/source files
src/{a2a3,a5}/.../aicpu/aicpu_executor.cpp	Remove ~1700 lines of inline scheduler methods, replace with sched_ctx_ member calls
src/{a2a3,a5}/.../runtime/shared/	Relocate runtime.cpp and pto_shared_memory.cpp
src/{a2a3,a5}/.../build_config.py	Host source_dirs changed to "runtime/shared"
src/{a2a3,a5}/platform/*/CMakeLists.txt	GLOB → GLOB_RECURSE, add missing copyright headers
docs/	4 docs updated with new paths and function references

[gemini-code-assist]

Code Review

This pull request refactors the AICPU runtime by extracting scheduler-related logic and state from the AicpuExecutor class into a new SchedulerContext class, with implementation files organized in a dedicated directory for better modularity. Documentation and build scripts are also updated to reflect these changes. The review feedback identifies several improvement opportunities: the use of recursive globbing in CMake could include unwanted files, hardcoded constants in scheduler_context.h should be moved to a shared header to avoid maintenance risks, a redundant query in the drain dispatch loop is inefficient, and an incorrect (void) cast exists for a variable that is actually used in the profiling path.