fix(scheduler): percent-based limit display shows raw fraction, not percent (bug-1831)

fmt_limit()/fmt_limit_units() formatted a percent-based limit's value
as a bare snprintf(..., "%f%%", limit->val.val) -- echoing the raw
stored value with a literal "%" appended. But xce_limit_val_t.val is
genuinely a 0-1 fraction when percent is set (confirmed end-to-end:
no /100 or *100 scaling exists anywhere in the config->capnp->runtime
pipeline; confirmed authoritative by the original hand-written C
literal this codebase's oldest percent-based limit was migrated from,
.val = 0.2 for a documented "20% mem cap"). A correctly-configured 20%
limit therefore displayed as "0.200000%" instead of "20.000000%" --
misleading, though technically an honest echo of the stored value.

Fixed by multiplying by 100.0 before formatting. Display-only --
update_limit_res_value()'s actual capacity computation was already
correct and is untouched. fmt_limit() (a thin XCE_UNITS_RAW wrapper)
inherits this fix for its own percent-branch output too, a deliberate,
intentional change from its pre-fix behavior for percent-based limits
specifically (its 5 pre-existing direct tests only assert rc > 0,
never the exact percent string, so this is safe).

Updated test_limit.c's percent-mode test fixture from an unrealistic
.val=80.0 to a realistic .val=0.8 (assertion text unchanged, since
0.8*100=80 either way) and test_repl_limit_table.c's own percent test
to expect its shared fixture's arbitrary .val=50.0 constant correctly
rendering as "5000.000000%". RED confirmed via the raw Unity testlog's
:FAIL: lines (the aggregate meson summary masks single-test failures,
a known harness quirk in this project); GREEN confirmed after, both
lib and scheduler suites, 0 Unity FAILs.

Discovered during live manual verification of scheduler-sim-diagnostics
Requirement 6 against a real deployed cluster.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RLSNJhNoULvVcUhXEFafQC

src/lib/testsuite/test_limit.c

@@ -455,7 +455,7 @@ static void test_fmt_limit_units_percent_limit_ignores_units_mode(void)
         .hosts       = NULL,
         .projects    = NULL,
         .val
-        = &(xce_limit_val_t) { .resname = "mem", .percent = 1, .val = 80.0 }
+        = &(xce_limit_val_t) { .resname = "mem", .percent = 1, .val = 0.8 }
     };
     char             buf[1024];
     xce_units_mode_t modes[] = { XCE_UNITS_RAW, XCE_UNITS_HUMAN,