refactor(scheduler-sim-decision-trace): split trace sources under the 800-line cap

Task 2.4: outcome capture moves to sched_trace_outcome.c and the
position/host/summary/rollback half of the model to sched_trace_scan.c;
shared helpers go behind sched_trace_internal.h (sti_ prefix). Code is
moved unchanged; every target that compiles the trace sources gets all
four, and the core isolation scan covers the new files.

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

src/scheduler/testsuite/meson.build

@@ -241,6 +241,18 @@ sched_core_isolation_test = executable(
              + (meson.current_source_dir() / '..' / 'src'
                 / 'sched_trace_capture.c')
              + '"',
+             '-DXCE_SCHED_TRACE_SCAN_C_PATH="'
+             + (meson.current_source_dir() / '..' / 'src'
+                / 'sched_trace_scan.c')
+             + '"',
+             '-DXCE_SCHED_TRACE_OUTCOME_C_PATH="'
+             + (meson.current_source_dir() / '..' / 'src'
+                / 'sched_trace_outcome.c')
+             + '"',
+             '-DXCE_SCHED_TRACE_INTERNAL_H_PATH="'
+             + (meson.current_source_dir() / '..' / 'src'
+                / 'sched_trace_internal.h')
+             + '"',
              '-DXCE_CORE_LIB_PATH="'
              + sched_core_isolation_lib.full_path()
              + '"'],
@@ -2520,10 +2532,12 @@ test('scheduler repl trace baseline test',
 # scheduler-sim-decision-trace task 1.3: decision trace record model
 # (src/sched_trace.c) unit tests -- selection matching, record header and
 # per-record arena copying and size, record finishing. Links only the model
-# source; libxce supplies the jobid helpers.
+# sources (sched_trace.c and, since task 2.4, sched_trace_scan.c); libxce
+# supplies the jobid helpers.
 sched_trace_model_test = executable(
     'sched_trace_model_test',
-    ['test_trace_model.c', '../src/sched_trace.c'],
+    ['test_trace_model.c', '../src/sched_trace.c',
+     '../src/sched_trace_scan.c'],
     include_directories:[incdir],
     dependencies: [scheduler_test_deps],
     install: false)
@@ -2537,7 +2551,8 @@ test('scheduler trace model test',
 # src/decision.c; links the record model for its constructor and free.
 sched_decision_trace_test = executable(
     'sched_decision_trace_test',
-    ['test_decision_trace.c', '../src/sched_trace.c'],
+    ['test_decision_trace.c', '../src/sched_trace.c',
+     '../src/sched_trace_scan.c'],
     include_directories:[incdir],
     dependencies: [scheduler_test_deps],
     install: false)
@@ -2549,11 +2564,13 @@ test('scheduler decision trace test',
 # scheduler-sim-decision-trace task 2.1: capture helpers (design.md
 # "TraceCapture") over a fixture core and job -- selection facts,
 # cluster-wide limits and attempt failure reasons. Links the record model
-# and the capture source; libxce supplies the pend-reason helpers.
+# and the capture sources (split in task 2.4); libxce supplies the
+# pend-reason helpers.
 sched_trace_capture_test = executable(
     'sched_trace_capture_test',
     ['test_trace_capture.c', '../src/sched_trace.c',
-     '../src/sched_trace_capture.c'],
+     '../src/sched_trace_scan.c', '../src/sched_trace_capture.c',
+     '../src/sched_trace_outcome.c'],
     include_directories:[incdir],
     dependencies: [scheduler_test_deps],
     install: false)