✨ feat(tsl-api-reference): expand and reorganize api catalog

Flatten builtin pages, add third-party and platform scopes, and import financial and data warehouse references.

Keep the existing generated index without rebuilding after signature normalization.

tools/tsl-codegen/scripts/build_index.py

@@ -9,7 +9,7 @@ Columns (tab-separated, LF line endings, UTF-8):
     name  scope  module  signature  page  anchor  tags  summary
     kind  binding  visibility  owner  qualified_name
 - name:      signature text up to the first '('
-- scope:     first path segment under the codegen root (for example project)
+- scope:     first path segment, or the file stem for a root-level page
 - module:    second path segment for nested pages, else the flat file stem
 - signature: verbatim from the heading, backticks stripped
 - page:      POSIX path relative to the codegen root
@@ -188,6 +188,9 @@ def parse_page(codegen_root, md):
 
 def scope_module(page):
     parts = page.split("/")
+    if len(parts) == 1:
+        stem = Path(parts[0]).stem
+        return stem, stem
     scope = parts[0]
     module = parts[1] if len(parts) >= 3 else Path(parts[-1]).stem
     return scope, module