chore(spec): regenerate spec-changes.json and the upgrade guide after merging main at 41d0d40 (step 18: 64 conversions, 324 semantic entries)

main added two step-18 semantic entries since 6729e10:
flow-builtin-node-config-undeclared-keys-refused (#22319) and
platform-global-object-organization-column-retired (#22331). At protocol 18
both generators project every step-18 entry, so both documents gain them.
The conversion ids are unchanged.

Claude-Session: https://claude.ai/code/session_01LAi5BVvQNiYzepSAcsoFLK
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude