test(scheduler-sim-eager-reconciliation): task 1.2 capture-safety unit coverage

Adds 3 tests proving guarantees that must hold under the widened
capture-eligibility gate: an already-captured job is never re-searched
or re-captured regardless of state (test_reconcile_still_skips_already_
captured_job_regardless_of_state), a PEND job with no match this round
stays uncaptured and remains eligible next round (test_reconcile_
no_match_leaves_pend_job_uncaptured_and_retries), and several
simultaneously outstanding jobs are captured independently with zero
cross-job interference (test_reconcile_multiple_jobs_captured_
independently_across_different_rounds).

Required making the shared add_job() fixture helper tolerant of -EEXIST
on a repeated queue registration (needed for the multi-job test, the
first in this file to call add_job() twice against the same core) --
traced to kvtab_add()'s narrowly-scoped -EEXIST return, provably a
no-op for all 11 pre-existing single-add_job()-call tests.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AgYRU3zDTqNGV5Jk8aiKLg

.kiro/specs/scheduler-sim-eager-reconciliation/tasks.md

@@ -9,7 +9,7 @@
   - _Requirements: 1.1, 3.1_
   - _Boundary: sim_reconcile_unaccounted_jobs_
 
-- [ ] 1.2 Extend unit coverage for capture-safety guarantees under the widened eligibility
+- [x] 1.2 Extend unit coverage for capture-safety guarantees under the widened eligibility
   - Add a test proving a job whose allocation was already captured is never re-searched or re-captured on a later round, regardless of its state
   - Add a test proving a job with no matching recorded decision this round stays uncaptured and remains eligible to be found on a later round
   - Add a test with several simultaneously outstanding jobs whose recorded dispatch decisions land in different rounds, proving each job's captured allocation reflects only its own recorded decision with no cross-job interference