Rename product, namespaces, libraries, paths, and assets from Orion/orion
to Onion/onion across the tree. TCP stack-shutdown magic is now ONIO
(0x4F4E494F) to match the corrected branding.
Add suites for liborion_platform (fs/log/notify), richer settings and ready
flag cases, and msg.hpp protocol ordinals. Link real platform sources under
ORION_HOST_TEST; fix DaemonCommands to unsigned so high-bit opcodes are
well-formed. Rename host binary to orion-host-tests.