Adds sched_on_job_array() (handler.c), a sibling case to
Data_data_schedjobs decoding the new Data.jobArray variant and
expanding it locally into N ordinary schedulable tasks via
base_jobid + i, routed through the existing unmodified per-job
pipeline (sched_on_jobs()). Each element gets its own deep clone
(clone_job_submit_data/clone_job_startinfo) of the shared submit
spec, since per-element teardown (free_Job_ptr) frees it
independently and a shared pointer would double-free.
Dedup reuses sched_get_job() against the same kvtab sched_add_job()
guards, rather than a new mechanism. A confirmation log line fires
once per successful expansion (skipped on a fully-duplicate
redelivery).
Adds a new task (5.3b) discovered during this task's review: the
shared wire dispatcher extract_data() (src/lib/request.c) has no case
for Data_data_jobArray and silently drops every real array push
before any receiver's handler runs -- outside every current task's
boundary, confirmed to affect the future API-server receive path
(task 5.4) identically. design.md's File Structure Plan corrected to
record this. User confirmed sequencing: fix it now, before 5.4.
Task 5.3 of job-array-single-wal-record (Requirements 6.3, 6.4, 6.5, 8.4).
Rongsong Shen
d16847185e