feat(scheduler-core): define new event payload types (task 7.2)

Adds JobStateChangeEvent (jobid/oldState/newState/exitCode) and
JobUpdateEvent (jobid/changedFields/job: Job) to controller.capnp,
matching design.md's spec verbatim. JobUpdateEvent.job reuses the
existing full 12-field Job/xce_job_t record, verified distinct from
the narrower SchedJob struct sharing the same mapname.

Extends ReplayEvent.body's union (task 7.1) with jobStateChange@10/
jobUpdate@11 -- the only two valid next ordinals, since capnp requires
strictly sequential ordinals with no gaps across a struct and task
7.1 deliberately stopped at @9. Existing @0-@9 fields and every other
struct in the schema are byte-identical.

Deep round-trip tests in test_e2e_capnp.c exercise every field with
non-default values, including the 3-level nested Job substructs
(submitData/allocs/pidinfo/pendreason). JOB_F_* bitmask bit values
deliberately left undefined -- a later task's job, not this
schema-only one's.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019dw5WnN3DXStaEaPYfACU1

.kiro/specs/scheduler-core/tasks.md

@@ -165,12 +165,13 @@
   - _Verified: 2026-08-04 — ReplayCluster/ReplayHeader/SnapshotEntry/ReplayEvent/SessionSummary/ReplaySession added fully; SnapshotData (empty {}) and ReplayDecision ({ts only}) added as compiler-mandated placeholders task 7.3 fills in (real fields for SnapshotData wholesale-replaced, a body union appended to ReplayDecision at new ordinals) since capnp's $C.codecgen has no per-struct opt-out from requiring the mapname'd C type to exist. ReplayEvent's union deliberately holds only the 9 members with pre-existing backing types (configPush/jobsPush/workersPush/resourcesPush/resvalsFull/resvalsDelta/queueUpdate/jobRusage/endSession); jobStateChange/jobUpdate deferred to task 7.2 as new ordinals — proven compiler-mandatory (not stylistic) by review, which independently confirmed capnp rejects both the AC 20 pseudocode's literal union syntax and any ordinal gap. Round-trip test (test_e2e_capnp.c) proven real via full clean rebuild (deleted+regenerated controller.capnp.{c,h}) both by implementer and reviewer. Full project build clean (controller/apiserver-CGO/scheduler/worker/xceadmin), 1075/1075 controller_unit_test passing, review APPROVED first pass with reviewer going beyond implementer's own verification (real capn_resolve()-omission and placeholder-removal breakage reproduced firsthand). Zero existing structs/fields touched._
   - _Depends: 6_
 
-- [ ] 7.2 Define new event payload types
+- [x] 7.2 Define new event payload types
   - Add the two genuinely new event payload message types (job state-change delta, job update delta with embedded full record) to the wire schema; every other event payload type reuses an existing wire message already used elsewhere in the schema
   - Observable: encoding a job state-change event and a job update event and decoding them back yields field-for-field equality with the original values
   - _Requirements: 5.20_
   - _Depends: 7.1_
   - _Boundary: ReplayFormat — not (P): 7.2/7.3/7.4 all edit the same schema file (controller.capnp); run sequentially to avoid concurrent edits to one file, even though each adds a logically disjoint set of structs_
+  - _Verified: 2026-08-04 — JobStateChangeEvent/JobUpdateEvent added to controller.capnp matching design.md's spec verbatim; JobUpdateEvent.job correctly reuses the full 12-field Job/xce_job_t record (not the narrower SchedJob sharing the same mapname — verified by field list). ReplayEvent.body's union extended with jobStateChange@10/jobUpdate@11, the only two valid next ordinals per task 7.1's baseline (capnp requires no gaps) — confirmed via a from-scratch capnp regeneration. Existing @0-@9 fields byte-identical. Deep round-trip tests (non-default values throughout, including 3-level nested Job substructs) prove the Observable; JOB_F_* bitmask values deliberately left undefined (later task's job). 1077/1077 controller_unit_test, full project build clean, review APPROVED first pass._
 
 - [ ] 7.3 Define decision payload types and the snapshot schema
   - Add the dispatch, pend, and preempt decision payload message types, reusing existing allocation and pend-reason wire messages where they already carry the needed fields