feat(job-array-one-based-index): classify every job submission first (task 2.1)

handle_jobsubmit classifies (first_jobid, array_size) before the field
checks, the before-event hook and any registry access: a tagged array
starting at index 0 is answered with the new E_XCE_ARRAY_START0 and an
ERROR log asking for the client to be upgraded (7.1, wins per 7.9);
size 0, tags 2/3, untagged multi-element submissions and arrays whose
last element exceeds 32767 (checked without addition) get -EINVAL.
Nothing is stored for a rejected submission. This also closes a crash:
a size-0 submission used to reach payload building and overflow calloc.
Existing array tests move to tagged block|1 first IDs.

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

.kiro/specs/job-array-one-based-index/tasks.md

@@ -25,7 +25,7 @@
   - _Boundary: IdgenArray_
 
 - [ ] 2. Controller: array admission and collision detection
-- [ ] 2.1 Classify every submission before any other check
+- [x] 2.1 Classify every submission before any other check
   - Add the distinct "array numbering starts at 1" error status and its message text to the shared error table
   - Classify a submission from its first ID and 64-bit size only: start-at-0 array first; then size 0, an unknown marking, an unmarked multi-element submission, and a last element above 32767 (computed without addition so no size can wrap)
   - Run the classification as the first step after the reply is initialised, before the existing field checks and the before-event hook; answer start-at-0 with the new status plus an ERROR log saying numbering starts at 1 and the client must be upgraded, and the other classes with invalid-argument; store nothing