Migrates argp_program_version in controller/main.c, scheduler/main.c,
and xce_test's test.c from the compile-time MK_VERSION/STR construction
to xce_compose_version(), computed into a static buffer and assigned
before argp_parse() runs (argp_program_version is a file-scope pointer,
not a constant expression it can be initialized from at compile time).
Each daemon's startup log now carries the identical version string
(never recomputed) on its first INFO line -- scheduler's BOTH
mutually-exclusive branches (--peers and no-peers), not just the one
literally named in the task text, since "when the daemon starts" is
unconditional.
Live-verified: --version and startup-log output are byte-identical for
both daemons across all branches. No remaining MK_VERSION callers
repo-wide.
Task 3.2/13 of build-time-versioning.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Rongsong Shen
88649a0462