feat(scheduler-sim-decision-trace): capture selection facts, cluster-wide limits and attempt reasons

Task 2.1: policy, queue and priority/queue-time ordering keys, each
matched cluster-wide limit as (name, scope), and per-code attempt
failure reasons with the hosts and resources they name, all copied into
the record arena.

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

src/scheduler/include/sched/trace.h

@@ -25,6 +25,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <time.h>
 
 #include "resreq.h"
 #include "sched/types.h"
@@ -212,6 +213,15 @@ typedef struct {
     int         count;
 } sched_trace_limit_tally_t;
 
+/* One cluster-wide limit matched to the job (2.3), from the schedobj's
+ * glimits. `scope` is the scope instance the limit applies to, as
+ * comma-separated `u=..,q=..,p=..` pairs; "" when the limit has no
+ * per-consumer scope. */
+typedef struct {
+    const char* limit; /* arena copy */
+    const char* scope; /* arena copy */
+} sched_trace_limit_ref_t;
+
 /* One requested resource of a single requirement or member (3.2). */
 typedef struct {
     const char* name; /* arena copy */
@@ -357,8 +367,21 @@ struct xce_sched_trace_rec_s {
     int                        line_bound;
     bool incomplete; /* arena growth failed: appending stopped */
 
-    /* selection block */
-    const char* policy_name; /* arena copy of ctl->policy_name, or NULL */
+    /* selection block (2.2, 2.3), filled by TraceCapture */
+    const char* policy_name;   /* the job's ordering policy: arena copy of
+                                * the queue's picker override, else of
+                                * ctl->policy_name, else of the core's
+                                * picker; NULL if none is known */
+    bool        selection_set; /* capture_selection ran: the ordering keys
+                                * below are known (not NOT_FOUND) */
+    const char* queue_name;    /* arena copy; NULL: the job has no queue */
+    int32_t     queue_priority;
+    int32_t     job_priority;
+    time_t      queue_time;
+    bool        glimits_set;   /* capture_glimits ran: the limits are known
+                                * (false: no schedobj, limits unavailable) */
+    int                      nglimits;
+    sched_trace_limit_ref_t* glimits; /* in the schedobj's glimits order */
 
     /* current requirement path (pushed and popped by the allocation chain) */
     sched_trace_path_t path;
@@ -560,4 +583,31 @@ extern void sched_trace_finalize_failed(xce_sched_trace_rec_t* rec, int err);
  */
 extern void sched_trace_search_end(xce_sched_trace_rec_t* rec, int rc);
 
+/*
+ * TraceCapture (src/sched_trace_capture.c, design.md "TraceCapture"). Each
+ * reads scheduler state on the thread that owns it, read-only, and copies
+ * what it reports into `rec` (never NULL: the SCHED_TRACE gate).
+ */
+
+/* The job's ordering policy and keys at selection (2.2): policy name, queue
+ * name and priority, job priority, queue time. A NULL job (not found by
+ * the allocator, 2.4) captures nothing. */
+extern void sched_trace_capture_selection(xce_sched_trace_rec_t*  rec,
+                                          const xce_sched_core_t* core,
+                                          const xce_sched_job_t*  job);
+
+/* The job's matched cluster-wide limits (2.3): each xce_vres_t in
+ * obj->glimits as (limit name, scope instance). A NULL obj (no schedobj,
+ * 2.4) leaves the limits unavailable. */
+extern void sched_trace_capture_glimits(xce_sched_trace_rec_t* rec,
+                                        const xce_sched_obj_t* obj);
+
+/* A failed compound attempt's reasons (3.5), from its pend-reason set before
+ * the scheduler replaces obj->reason: one ATTEMPT_REASONS entry with a
+ * count per pend-reason code (main reason, host and resource reasons, in
+ * the order first seen) and the distinct hosts and resources they name.
+ * A NULL or empty set stores the entry with no reasons. */
+extern void sched_trace_capture_attempt_reasons(xce_sched_trace_rec_t*  rec,
+                                                const xce_pendreason_t* reason);
+
 #endif