feat(scheduler-sim-decision-trace): emit traces inline and apply settings at session boundaries

Task 4.6: session begin makes the next settings current, stamps the
session number and publishes them to the core; session end withdraws and
releases them. Emission marks the round traced, flushes the collapsed
range and reprints the suppressed echo in continue mode, renders to the
console and the trace file with identical bytes, and stores the record.
sim_print_decision is exported unchanged.

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

src/scheduler/meson.build

@@ -33,6 +33,7 @@ scheduler_srcs = [
   'src/repl_trace_render_outcome.c',
   'src/repl_trace_store.c',
   'src/repl_trace.c',
+  'src/repl_trace_emit.c',
   'src/schedobj.c',
   'src/plugin.c',
   'src/resource.c',