Add opt-in CLI execution report files

docs/internal/adapters.md

@@ -77,6 +77,10 @@ The report collector is per invocation. It ignores nonterminal events and
 copies terminal aggregates once, including usage presence and completeness.
 It retains no history or shared state; adapters decide whether to attach it and
 how to present its snapshot.
+CLI `run` attaches one only when a report path is selected, writes generated
+output first on success, and then writes the terminal snapshot when present.
+Its report path remains untouched for pre-invocation failures or absent
+terminal observations; report and artifact writes are independent.
 
 ## Package-Local Guarantees