feat(incremental): wire maintained tier behind views; rebuild fallback (WP-0011 T4)

Route InformationSpace.all_pages through a maintained UnionIndex: equivalence is
served from the incrementally maintained index (curator bindings re-synced live
from the log fold + detected content edges), exposed in decision-log string form
so results are a behaviour-preserving superset. The index is built lazily and
rebuilt (bounded fallback) when the union mutates (attach/edit invalidate it);
reindex() forces a rebuild and verify_index() runs the I-2 self-healing checker.
all_pages() gains an optional equivalence_groups source (default = fold) so
direct callers are unaffected. SCOPE updated; WP-0011 done. 173 tests green.

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

workplans/SHARD-WP-0011-incremental-union.md

@@ -4,7 +4,7 @@ type: workplan
 title: "incremental union maintenance + equivalence index + I-2 verification"
 domain: whynot
 repo: shard-wiki
-status: active
+status: done
 owner: tegwick
 topic_slug: whynot
 created: "2026-06-15"
@@ -41,7 +41,7 @@ deployment is later.
 
 ```task
 id: SHARD-WP-0011-T1
-status: todo
+status: done
 priority: high
 state_hub_task_id: "842f480b-7b14-47cd-818b-012dbda9c187"
 ```
@@ -55,7 +55,7 @@ unrelated pages don't; verified edges match a brute-force oracle on a small corp
 
 ```task
 id: SHARD-WP-0011-T2
-status: todo
+status: done
 priority: high
 state_hub_task_id: "2da4e0b8-22cc-4ad1-a9aa-b5e991515d30"
 ```
@@ -70,7 +70,7 @@ stale edge.
 
 ```task
 id: SHARD-WP-0011-T3
-status: todo
+status: done
 priority: high
 state_hub_task_id: "b602ce31-ad9a-4c7f-b596-f039722373fc"
 ```
@@ -85,7 +85,7 @@ equivalent event orders.
 
 ```task
 id: SHARD-WP-0011-T4
-status: todo
+status: done
 priority: medium
 state_hub_task_id: "2f3d083c-0b2e-4b58-9e96-c0461c5eb089"
 ```