fix(agent-tools, setup): standardize metadata keys to lowercase and update HTML ingestion

- Renamed `partIndex`/`totalParts` to `partindex`/`totalparts` in `section_retriever.ts`, `spec_retriever.ts`, and document creation logic.
- Adjusted sorting logic to use the new `partindex` field.
- Updated metadata handling and string interpolation to reference the lowercase keys.
- Fixed import path for `HTMLTextSplitter` and moved the file to `setup/textsplitters/HtmlTextSplitter.ts`.
- Added HTML preprocessing utilities (`addNewlinesAfterBlocks`, `convertTablesToMarkdown`) in ingestion workflow.
- Integrated table-to‑markdown conversion and newline insertion to improve text splitting and document structure.

setup/textsplitters/index.ts

@@ -0,0 +1 @@
+export * from "./HtmlTextSplitter";