v0.4: align kernel state, body semantics, and memory-space docs

[zhoubot]

Summary

• clarify canonical .brg vs local memory-space semantics for kernel loads/stores
• make vector memory addressing explicitly per-lane and align the Sail model with that rule
• align v0.4 SIMT/kernel documentation around block/body control flow, p/mask semantics, and LB*/LC* state treatment
• regenerate v0.4 machine-readable state/docs and update linked LinxCore architecture notes
• repin rtl/LinxCore to pick up the two-layer block-contract documentation update

Validation

• python3 tools/bringup/check_linxcore_arch_contract.py --root /home/zhoubot/linx-isa --strict

Notes

• The older check26_contract.py path referenced in the local skill is not present in this checkout, so it could not be run from here.