Add configurable topdata wiki visibility policy (#4)

## Summary
- add YAML-backed generated wiki visibility policies for topdata datasets
- centralize page and reference eligibility through a visibility index
- cover eligibility helpers, metadata precedence, derived feat sets, and link suppression with toolkit tests

## Verification
- go test ./...
- module ./validate-topdata.sh with the feature toolkit binary
- module ./build-wiki.sh --force with the feature toolkit binary

Companion module branch: codex-wiki-visibility.

Reviewed-on: https://gitea.westgate.pw/ShadowsOverWestgate/sow-tools/pulls/4
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

internal/project/project_test.go

@@ -273,6 +273,7 @@ topdata:
     link_strategy: preserve_westgate_wiki_links
     namespaces_file: namespaces.yaml
     tables_file: custom-tables.yaml
+    visibility_file: visibility.yaml
     templates_dir: templates
     manual_sections_dir: manual-sections
     deploy_manifest: wiki-manifest.json
@@ -347,6 +348,9 @@ autogen:
 	if got, want := effective.TopData.Wiki.TablesFile, "custom-tables.yaml"; got != want {
 		t.Fatalf("expected wiki tables file %q, got %q", want, got)
 	}
+	if got, want := effective.TopData.Wiki.VisibilityFile, "visibility.yaml"; got != want {
+		t.Fatalf("expected wiki visibility file %q, got %q", want, got)
+	}
 	if got, want := effective.TopData.Wiki.TemplatesDir, "templates"; got != want {
 		t.Fatalf("expected wiki templates dir %q, got %q", want, got)
 	}
@@ -876,6 +880,7 @@ func TestValidateLayoutRejectsInvalidTopDataWikiConfig(t *testing.T) {
 					StatusListingScope: "global",
 					NamespacesFile:     "../namespaces.yaml",
 					TablesFile:         "../tables.yaml",
+					VisibilityFile:     "../visibility.yaml",
 					TemplatesDir:       ".",
 					ManualSectionsDir:  "../manual",
 					StalePages: TopDataWikiStalePagesConfig{
@@ -898,6 +903,7 @@ func TestValidateLayoutRejectsInvalidTopDataWikiConfig(t *testing.T) {
 		"topdata.wiki.status_listing_scope",
 		"topdata.wiki.namespaces_file",
 		"topdata.wiki.tables_file",
+		"topdata.wiki.visibility_file",
 		"topdata.wiki.templates_dir",
 		"topdata.wiki.manual_sections_dir",
 		"topdata.wiki.stale_pages.default",