DADBEAR unit21: route supersession audit to decide

[adamlevineagent]

Summary

• keep supersession audit writes but compile affected nodes directly into DADBEAR TRACE->DECIDE work
• remove the record_supersession dependency on the legacy staleness queue enqueue path
• add proof that supersession recording creates DECIDE work while leaving pyramid_staleness_queue empty

Verification

• cargo test --lib record_supersession_compiles_decide_work_without_legacy_queue -- --nocapture
• cargo test --lib edge_survives_endpoint_supersession -- --nocapture
• cargo test --lib faq_link_survives_related_node_supersession -- --nocapture
• cargo test --lib targeted_evidence_resolves_real_source_not_placeholder -- --nocapture
• cargo test --lib stale_check_decision_ -- --nocapture
• cargo test --lib test_set_file_content_hash_preserves_node_ids_order_independent -- --nocapture
• cargo test --lib not_stale_pass_naturally_terminates_without_execute -- --nocapture
• cargo test --lib skip_abstain_naturally_terminates_without_execute -- --nocapture
• cargo check --lib --message-format short
• git diff --check

Note: the full guard script exited 0; terminal output was large/truncated but included the final cargo check success. After restoring accidental cargo fmt --all noise, the focused supersession test + cargo check + diff-check were rerun and passed.