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>

tests/test_incremental_wiring.py

@@ -0,0 +1,74 @@
+"""Wire the incremental tier behind InformationSpace views (SHARD-WP-0011 T4)."""
+
+from shard_wiki.adapters import FolderAdapter
+from shard_wiki.coordination import EventType
+from shard_wiki.model import Identity
+from shard_wiki.space import InformationSpace
+from shard_wiki.views import all_pages
+
+
+def _shard(tmp_path, name, files):
+    root = tmp_path / name
+    for rel, text in files.items():
+        p = root / rel
+        p.parent.mkdir(parents=True, exist_ok=True)
+        p.write_text(text, encoding="utf-8")
+    return FolderAdapter(name, root)
+
+
+def test_all_pages_via_index_matches_direct_fold(tmp_path):
+    space = InformationSpace("space")
+    space.attach(_shard(tmp_path, "wiki", {"Home.md": "welcome", "Guide.md": "the guide"}))
+    space.attach(_shard(tmp_path, "notes", {"Daily.md": "today"}))
+    # Routed-through-index result equals the direct fold-based computation (behaviour unchanged).
+    via_index = {(e.name, e.members) for e in space.all_pages()}
+    direct = {(e.name, e.members) for e in all_pages(space.union)}
+    assert via_index == direct
+
+
+def test_curator_binding_collapses_via_maintained_index(tmp_path):
+    space = InformationSpace("space")
+    space.attach(_shard(tmp_path, "a", {"Foo.md": "x"}))
+    space.attach(_shard(tmp_path, "b", {"Bar.md": "y"}))
+    space.log.append(
+        "space", EventType.BINDING_MADE, {"members": ["a:Foo", "b:Bar"]}
+    )
+    # The maintained index re-syncs curator edges live from the log fold.
+    collapsed = [e for e in space.all_pages() if len(e.members) == 2]
+    assert len(collapsed) == 1
+    assert set(collapsed[0].members) == {Identity("a", "Foo"), Identity("b", "Bar")}
+
+
+def test_content_duplicate_collapses_via_index(tmp_path):
+    space = InformationSpace("space")
+    space.attach(_shard(tmp_path, "a", {"Foo.md": "the very same body content here"}))
+    space.attach(_shard(tmp_path, "b", {"Bar.md": "the very same body content here"}))
+    dup = [e for e in space.all_pages() if len(e.members) == 2]
+    assert len(dup) == 1  # content equivalence detected by the maintained index
+    assert set(dup[0].members) == {Identity("a", "Foo"), Identity("b", "Bar")}
+
+
+def test_attach_invalidates_index(tmp_path):
+    space = InformationSpace("space")
+    space.attach(_shard(tmp_path, "a", {"Foo.md": "same body"}))
+    assert space.all_pages()  # builds the index (one page, no groups)
+    space.attach(_shard(tmp_path, "b", {"Bar.md": "same body"}))  # marks index stale
+    dup = [e for e in space.all_pages() if len(e.members) == 2]
+    assert len(dup) == 1  # rebuilt fallback picks up the new equivalent page
+
+
+def test_verify_index_reports_healthy_when_consistent(tmp_path):
+    space = InformationSpace("space")
+    space.attach(_shard(tmp_path, "a", {"Foo.md": "same body"}))
+    space.attach(_shard(tmp_path, "b", {"Bar.md": "same body"}))
+    space.all_pages()  # ensure built
+    report = space.verify_index()
+    assert report.healthy is True
+
+
+def test_reindex_is_an_explicit_fallback(tmp_path):
+    space = InformationSpace("space")
+    space.attach(_shard(tmp_path, "a", {"Foo.md": "content"}))
+    before = space.index.digest()
+    space.reindex()
+    assert space.index.digest() == before  # rebuild is deterministic