Cover host-info command builder

[midwan]

Summary

• extract the host-info shell command into a testable command header
• add command-builder coverage for the host-info shell snippet
• enable strict prototype warnings for target builds
• convert local no-argument helpers to explicit void prototypes

Validation

• make -B test HOST_CFLAGS="-std=c99 -Wall -Wextra -Wstrict-prototypes -Werror -Isrc"
• git diff --check
• make -n all