Measure output capture allocations for chunked writes

docs/roadmap/remediation.md

@@ -1,6 +1,6 @@
 # Performance Implementation Remediation
 
-**Status:** Remediation in progress; R1–R2 complete.
+**Status:** Remediation in progress; R1–R3 complete.
 
 **Review baseline:** df064bd, reviewed on 2026-10-09 against the
 [performance target](performance.md) and
@@ -126,6 +126,13 @@ design; these findings do not require disk-backed diagnostics or a memory cap.
 and confirm captured bytes and forwarding remain correct. Report allocation
 results as workload-specific measurements with no numerical runtime guarantee.
 
+**Completion:** Complete. The benchmark now includes equal 8 MiB output in one
+write and 32 KiB chunks, with untimed byte-for-byte capture and forwarding checks.
+Three repetitions passed and measured about 8.39 MB/2 allocations and
+16.74 MB/10 allocations respectively. Go-output documentation and implementation
+results qualify the single-write figures and distinguish allocation totals,
+retained output, and unmeasured peak memory.
+
 ## R4: Reconcile Feature And Implementation Status
 
 **Priority:** Low.