docs(saved-filters,dashboard,system,series): Beam WO3 batch 5 — 15 endpoints + dedupe

Beam drafted 15 frontmatter'd docs (saved-filters CRUD, dashboard
sections/preferences/restore, system config/settings, series list + books);
Claude verified shapes against handlers and pinned the registry:
- saved-filters: SavedFilterResponse pinned by type (RFC3339 timestamps here,
  unlike most of the API); create/update share CreateSavedFilterRequest
  (resource_type oneof media-items|collections|devices)
- dashboard: preferences GET pin {hidden_collections, collection_order,
  items_per_section}; PUT returns full UserDashboardPreferences row; sections
  wrapper {sections}
- system: GET+PUT /api/system/config are admin-defined key/value maps — new
  AnyJSONObject sentinel (gate shape-checks without key comparison; request
  side too). UpdateSystemConfiguration returns {status, message} — verified,
  not guessed. GET /api/system/settings returns []SettingEntry.
- series: {series[{name, library_id, book_count, total_in_series,
  cover_paths, last_entry_at}], total, limit, offset}; books by
  ?name=&library_id= with family-lens 403

Dedupe: deleted dashboard.md, system/config.md, system/settings.md — each
covered the same endpoints as Beam's per-endpoint files (content merged by
the gate-verified shapes; old prose recoverable from git).

Beam clarifications confirmed: scanner routes are WO5 (docs exist);
progress/books-match are WO5.

internal/docs/drift_test.go

@@ -221,6 +221,15 @@ func validateRequestExample(t *testing.T, doc *APIDoc, schema Schema) {
 		return
 	}
 
+	// AnyJSONObject request: arbitrary keys (config maps). Shape-check only.
+	if _, ok := schema.Request.(AnyJSONObject); ok {
+		var m map[string]json.RawMessage
+		if err := json.Unmarshal(doc.ExampleRequest, &m); err != nil {
+			t.Errorf("%s: example-request must be a JSON object", doc.RelPath)
+		}
+		return
+	}
+
 	// Typo guard: field names must exist on the bind struct.
 	dec := json.NewDecoder(bytes.NewReader(doc.ExampleRequest))
 	dec.DisallowUnknownFields()
@@ -257,6 +266,16 @@ func validateResponseExample(t *testing.T, doc *APIDoc, schema Schema) {
 		return
 	}
 
+	// AnyJSONObject: response is an object with arbitrary/dynamic keys
+	// (e.g. map[string]string config). Only shape-check, never key-check.
+	if _, ok := schema.Response.(AnyJSONObject); ok {
+		var m map[string]json.RawMessage
+		if err := json.Unmarshal(doc.ExampleResponse, &m); err != nil {
+			t.Errorf("%s: example-response must be a JSON object", doc.RelPath)
+		}
+		return
+	}
+
 	want, isSlice := responseTopLevelKeys(t, schema.Response)
 
 	var got map[string]bool