Bundled zcnblk client source

These four build inputs are vendored from the repository's canonical client edge implementation so Helm can install on a node without a source checkout:

• kmods/zcnblk_client_mod.c
• kmods/zcnblk_shm_abi.h
• zccusan/deploy/zcblock-csi/zcnblk-client-only.mk as Makefile
• zccusan/deploy/zcblock-csi/zcnblk-client-only.kbuild as Kbuild, for kernels that generate an external-module output Makefile

Before packaging the chart, update these copies and verify them with cmp. They must remain byte-for-byte identical to the canonical inputs.