Replace the single-attempt subtask loop with the 3-attempt retry
ladder from orchestrator-sub-agent.ts:128-206 (sequential path).
Attempt 1: reduced_complexity=false, minimal_skills=false
Attempt 2: reduced_complexity=(tier==Basic), minimal_skills=false
Attempt 3: reduced_complexity=true, minimal_skills=true
Retryable = error.is_some() && node_count==0 && !abort.is_set()
&& !is_non_retryable(&err). The non-retryable predicate
is evaluated once from attempt-1's error (faithful to TS).
Partial results (node_count>0) are never retried.
After 3 still-zero the existing zero_node_failure stop applies.
Abort classification preserved.
4 new tests; existing run_zero_node_subtask_stops_and_errors updated
to supply 3 garbage responses (the ladder now consumes up to 3).
166 tests green; clippy + fmt clean; run.rs at 764 lines.
08d6feb601