spec(SHARD-WP-0006 T5): track §C as O-8..O-12; refresh decisions/traceability; close-out

Adds O-8 (preset bundles), O-9 (shard sharing vs tenant partition), O-10
(span authz + transclusion ⊕), O-11 (union under unavailability), O-12
(append-log throughput) to §12. Refreshes §14 decisions (event-sourced
coordination, conformance, I-2 verification) and §16 traceability (round-2
review + WP-0006). Flips SHARD-WP-0006 done.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

workplans/SHARD-WP-0006-architecture-hardening-2.md

@@ -4,7 +4,7 @@ type: workplan
 title: "core architecture hardening II (round-2 review fixes)"
 domain: whynot
 repo: shard-wiki
-status: active
+status: done
 owner: tegwick
 topic_slug: whynot
 created: "2026-06-15"
@@ -113,7 +113,7 @@ add the conformance obligation to the acceptance posture.
 
 ```task
 id: SHARD-WP-0006-T4
-status: todo
+status: done
 priority: medium
 state_hub_task_id: "adf4ed28-8338-49ed-a552-c9fbe11c43ee"
 ```
@@ -132,7 +132,7 @@ not merely asserted; on mismatch, recompute the affected partition. State that I
 
 ```task
 id: SHARD-WP-0006-T5
-status: todo
+status: done
 priority: medium
 state_hub_task_id: "18cb718a-e507-41d0-ae14-b144a56e3d57"
 ```