Extract helper functions _supplement_executing and _supplement_completed
to flatten the nested conditional logic. This improves readability and
makes the code easier to test and maintain.
Addresses code review finding: supplement_decision_logs nested complexity
Add `deleted` terminal status: completed/cancelled/failed → deleted via
DELETE /api/intelligent-evals/{id} (idempotent, 409 for non-terminal).
Deleted evals are hidden from list, detail, stats, and all sub-resource
endpoints (sessions/report/decision-logs/config-snapshots); child tables
are untouched (audit-safe). Frontend shows a Popconfirm-guarded delete
button for terminal evals only.
create_decision_log now checks for an existing log with the same
(eval_id, decision_type, context) tuple before inserting. If found, it
returns the existing row's dict instead of appending a duplicate. The
append-only audit invariant is preserved (a worker that re-emits the
same decision within a single minute no longer produces duplicate rows).
Removed the xfail guard in test_decision_log_immutability; the test
now passes (3 identical POSTs → 1 DB row).
