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>

.kiro/specs/scheduler-sim-decision-trace/tasks.md

@@ -194,7 +194,7 @@
   - _Requirements: 2.1, 2.4, 2.5, 3.1, 3.2, 4.3, 5.1, 5.9, 6.1, 6.2, 6.3, 6.4, 7.6, 7.7, 9.2, 9.3, 9.4_
   - _Boundary: TraceRenderer_
 
-- [ ] 4.2 Store the latest trace per job and serve info trace, test first
+- [x] 4.2 Store the latest trace per job and serve info trace, test first
   - **Storing:** a new trace for a job replaces its earlier one.
   - **Memory bound:** accounted from each record's size.
     - At 64 MiB, the oldest traces are evicted, never the newest.
@@ -365,3 +365,4 @@
 - 3.3: the pre-filter (`sched_host_iter_next`) opens a host scope (`sched_trace_host_begin`) for every candidate and closes it with a verdict on each rejection: SELECT (pre-filter), INTERNAL(rc) for an uncommitted-fetch or check error, from-rows for a resource rejection (unreachable from the runner). A host the iterator returns is left in an open scope with no entry, so 3.4 must end or replace it for the accepted, already-claimed, snapshot-failure and per-host-error paths, or later rows attach to a stale host. A scan stopped with rc<0 calls `pos_scan_error`; exhaustion does not. `unsatisfy_` hands every row to `sched_trace_check_rows`. The sim thread's reconciliation reaches that hook but sees trace_rec NULL.
 - 3.4: runner hooks are in alloc_runner.c. The 1.5 OPEN item is settled: `sched_trace_no_plan` counts `reqs_none_generated` once and sets `scope_no_plan`, after which `search_end` makes no statement and `resreq_begin`/`search_end` reset the flag. So a declined or generator-failed requirement has a NO_PLAN entry and no SEARCH_END line, and 4.1 must render the NO_PLAN line as "no plan generated: <reason>". The 3.3 open scope is closed: every returned candidate gets a fresh host scope and one verdict, and check_begin drops any stale host rows. When the iterator can't start, the position ends as SCAN_ERROR with err 0, so 4.1 must render a scan error with no code. trace.h is at 790 lines; split it before adding to it.
 - 4.1: the renderer is `repl_trace_render(rec, units, out1, out2)`, declared in repl_internal.h, in repl_trace_render.c plus repl_trace_render_outcome.c, with a private repl_trace_render.h. It renders once per sink, so the bytes are identical. Amounts use `repl_format_numeric_resource_value` ("8.00 GB" in human mode) and times use `repl_format_ts_human`. Wording where the design is silent is fixed by the golden tests in test_trace_render.c, so 4.2/4.6/6.1 must reuse the renderer, never re-format. Pend-reason arrays may contain NULL entries (capture keeps them); every walk must skip them. The renderer is not yet in sched_sim_isolation_lib or the sim isolation scan list (5.1).
+- 4.2: the store API is `repl_trace_store_put`, `repl_trace_store_bytes`, `repl_cmd_info_trace` and `repl_trace_store_fini` (an addition; nothing calls it at shutdown yet, so 4.5/4.6/5.2 must). `xce_repl_trace_state_t` (repl_internal.h) holds only the store fields; 4.3 adds next/cur/session flags to it. The 1.3 "file tag" is dropped: `info trace` is console-only (Req 8.1) and emission writes through the session's `cur` settings. `info trace` is not yet routed from repl_cmd_info (5.2). Open (6.2): an `id_list_add` OOM can silently drop array elements from a listing.