Roll the repository content back to the d716033b 'migrate Falcores kernel
architecture' version, but with the repository shrunk so the platform
accepts the submission. Fast-forward commit on top of 53aecb31 (no force
push needed; main is protected).

Tree equals commit 40f9416:
- re-applies the migrated architecture (arceos/, crates/, kernel/, src/)
- drops local-only large assets from tracking: rootfs/ (297 MiB),
  testcase/ (51 MiB), img-data/ (26 MiB), Falcores总结汇报PPT.pptx,
  初赛设计文档.pdf, .logs/ (see .gitignore and README for restore steps)
- final tracked tree is ~36 MiB vs ~424 MiB at d716033b

The online final evaluation (final-testcode: buildstorm + cagent on
riscv64/loongarch64) builds kernel-rv/kernel-la via 'make all' and uses
the platform-provided sdcard image as the root filesystem, so none of the
removed local assets are needed for the evaluation.