feat(scheduler-controller-msg-gap): route notify job-update to in-place sched_update_existing_job (task 5.6, bug-765 G-8+G-4)

The notify schedUpdateJob path shared XCE_SCHED_OP_UPDATE_JOB with the
dataset bulk-load, so the dequeue routed both to sched_update_jobs()
(create/replace) — a notify update to an existing job corrupted/duplicated
live job state and never returned -ENOENT (Req 3 UB-3.1/UB-3.2 unmet;
sched_update_existing_job was dead code copying only state).

- Add distinct op XCE_SCHED_OP_UPDATE_JOB_FIELDS (+ jobfieldsupdate union),
  enqueued only by the notify handler, dequeued to sched_update_existing_job.
- Move sched_update_existing_job to schedobj.c; update all mutable fields
  (state, priority, queue, resreq) in place; -ENOENT unknown, -EINVAL NULL.
- Dataset bulk-create path unchanged. Killer frees the new payload.
- New white-box test sched_job_update_test (3/3); regression sched_test 15/15.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.kiro/specs/scheduler-controller-msg-gap/tasks.md

@@ -64,10 +64,10 @@ Wire the five new op types into the `switch (req->op)` in `sched_update()`, impl
 - [x] 5.2 Add `XCE_SCHED_OP_UPDATE_RESOURCES` case — iterate `resdata->resources[]`, call `makeResource(sched->resmgr, r)` for each non-NULL entry
 - [x] 5.3 Add `XCE_SCHED_OP_UPDATE_RESVALS_FULL` case — iterate `resvaldata->vals[]`, find resource in `sched->resmgr` by name, update value; log WARN and skip unknown resources
 - [x] 5.4 Add `XCE_SCHED_OP_UPDATE_RESVALS` case — iterate `resvals->vals[]`, find worker by host name via `sched_get_worker()`, update worker's `resvals` zarray; silently skip unknown hosts
-- [x] 5.5 Add `XCE_SCHED_OP_JOB_RUSAGE` case — find job by jobid, store rusage data, call `plugin_job_rusage_update()`; return `-ENOENT` if job not found
-- [x] 5.6 Implement `sched_update_existing_job()` — find job by jobid via `sched_get_job()`, update mutable fields (state, priority, allocs), call `plugin_job_update()`; return `-ENOENT` when jobid is unknown
+- [ ] 5.5 Add `XCE_SCHED_OP_JOB_RUSAGE` case — find job by jobid, **store rusage data ON THE JOB** (`xce_job_rusages_t`/`xce_sched_job_rusages_t` field added to `xce_sched_job_t`, replacing any prior, freed in `kill_sched_job`), call `plugin_job_rusage_update()`; return `-ENOENT` if job not found. _Remediation (bug-765, gap G-5): rusage was never stored — `xce_sched_job_t` has no rusage field; Req 6 UB-6.1 unmet. See research.md §Gap Re-Audit._
+- [x] 5.6 Implement AND WIRE `sched_update_existing_job()` — find job by jobid via `sched_get_job()`, update ALL mutable fields per Req 3 (state, priority, queue, resource request — resreq string realloc like `sched_update_existing_queue`), call `plugin_job_update()`; return `-ENOENT` when jobid unknown, `-EINVAL` on NULL. **CRITICAL routing fix:** the notify `schedUpdateJob` handler (`sched_handle_sched_update_job`, handler.c:200) and the dataset bulk-load (`sched_on_jobs`, handler.c:31) BOTH enqueue `XCE_SCHED_OP_UPDATE_JOB`, and the dequeue (scheduler.c:755) routes BOTH to `sched_update_jobs()` (create/replace). Distinguish the notify path (introduce a distinct op, e.g. `XCE_SCHED_OP_UPDATE_JOB_FIELDS`, enqueued only by the notify handler, dequeued to `sched_update_existing_job`) so a notify update mutates-in-place / returns `-ENOENT` and NEVER creates a job (Req 3: jobs created only via the dataset path). _Remediation (bug-765, gap G-8+G-4): `sched_update_existing_job` was dead code (0 callers) and copied only `state`; UB-3.1/UB-3.2 unmet. See research.md §Gap Re-Audit._
 - [x] 5.7 Add WARN log in `sched_update()` after switch block for non-zero `rc` — include symbolic op name via `xce_sched_op_name()` and `strerror(-rc)`
-- [x] 5.8 Extend `sched_pend_update_killer` with no-op cases for all five new op types to suppress unhandled-case compiler warnings
+- [ ] 5.8 Free new-op payloads in `sched_pend_update_killer` (and any dequeue early-exit) for all new op types (`UPDATE_QUEUE`/`UPDATE_RESOURCES`/`UPDATE_RESVALS_FULL`/`UPDATE_RESVALS`/`JOB_RUSAGE`/the new `UPDATE_JOB_FIELDS`) — ownership IS transferred to the request (handler nullifies the notify/dataset payload pointers), so the empty `break;` cases leak. Use the lib deep-free helpers; validate ASAN-clean (no double-free). _Remediation (bug-765, gap G-3): killer had no-op `break` cases → confirmed per-message leak. See research.md §Gap Re-Audit._
 
 ---
 
@@ -125,3 +125,6 @@ Extend `src/scheduler/testsuite/test.c` with unit tests covering every acceptanc
 - [x] 9.7 Test dequeue path for `XCE_SCHED_OP_JOB_RUSAGE` — verify `-ENOENT` for unknown jobid, rusage stored and plugin called for known jobid; verify `-EINVAL` on NULL rusage
 - [x] 9.8 Verify dead code symbols are absent — compile-time check that `sched_handle_jobpush` / `sched_handle_workerpush` are not defined (2.1, 2.2)
 - [~] 9.9 *(gated: log capture infrastructure)* Verify WARN log is emitted in `sched_update()` when any handler returns a non-zero error code (optional — may require log capture infrastructure)
+
+## Implementation Notes
+- 5.6 (bug-765 remediation, gaps G-8+G-4, done 2026-06-18): Introduced a distinct op `XCE_SCHED_OP_UPDATE_JOB_FIELDS` (+ `jobfieldsupdate.job` union member) so the notify `schedUpdateJob` handler routes to `sched_update_existing_job` (now in schedobj.c) which mutates state/priority/queue/resreq IN PLACE and returns `-ENOENT` for unknown jobid — never creating a job. The dataset bulk-create path (`sched_on_jobs` → `XCE_SCHED_OP_UPDATE_JOB` → `sched_update_jobs`) is unchanged. Killer frees the new op's payload via `free_Job_ptr`. New white-box test `testsuite/test_job_update.c` (separate meson executable `sched_job_update_test`, white-box `#include "../src/schedobj.c"` + stubs for scheduler-internal externs): 3/3 PASS, regression `sched_test` 15/15, ASAN clean (leaks-off per suite convention). VERIFY NOTES: (1) the handler→dequeue ROUTING is verified by code review, NOT an automated integration test (an end-to-end test through `sched_handle_notify` needs NotifyData capnp plumbing — follow-up); (2) `free(job->resreq)` on replace is shallow but consistent with the codebase — `kill_sched_job` is a no-op stub, so sched jobs are not deep-freed anywhere; the inner-resreq leak is pre-existing, not introduced here. (3) test_job_update.c originally had an accidental `*/` inside a comment (`make_*/kill_*`) + non-ASCII chars + a `make_sched_obj` stub conflicting with the static def in schedobj.c — rewritten ASCII-clean with correct stub set. Task 9.4 (test sched_update_existing_job) is now genuinely satisfied by this real test.