feat(scheduler-sim-decision-trace): store the latest trace per job and serve info trace

Task 4.2: a new trace replaces a job's earlier one; above 64 MiB the
oldest traces are evicted (never the newest) and marked discarded until
a newer capture; info trace renders a job's or an array's stored traces
in the current units mode, or reports discarded / no trace with the
job's state / unknown job.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/scheduler/meson.build

@@ -31,6 +31,7 @@ scheduler_srcs = [
   'src/repl_params.c',
   'src/repl_trace_render.c',
   'src/repl_trace_render_outcome.c',
+  'src/repl_trace_store.c',
   'src/schedobj.c',
   'src/plugin.c',
   'src/resource.c',