Adds fmt_limit_units(buf, len, limit, units_mode) to src/lib/xcelimit.c,
a units-mode-aware sibling of fmt_limit() following the
fmt_jobid()/fmt_jobid_ex() extended-sibling pattern. Reuses fmt_limit()'s
exact consumer-dump loop untouched; only the final value line branches:
percent limits always render bare "%f%%" regardless of mode, byte-valued
(or "swp"-special-cased) absolute values render via
xce_format_units_value() (task 7), everything else keeps the
unconditional "%f".
fmt_limit() itself is now a one-line XCE_UNITS_RAW wrapper around
fmt_limit_units() -- provably byte-identical to its prior output for
every input shape, so its 5 existing direct unit tests needed zero
changes (the regression proof this refactor relies on).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RLSNJhNoULvVcUhXEFafQC
