feat: Track the table extraction method (#4346)
<!-- CURSOR_SUMMARY -->
> [!NOTE]
> **Low Risk**
> Adds a new optional metadata field and wires it through PDF
partitioning; behavior is additive and low risk aside from potential
downstream consumers expecting a fixed metadata schema.
>
> **Overview**
> **Adds table-provenance metadata for extracted tables.**
`ElementMetadata` now includes an optional `table_extraction_method`
(e.g., `grid`, `tatr`, `vlm`) and includes it in metadata consolidation.
>
> During PDF partitioning, the value is propagated from each
`LayoutElement` onto the resulting element metadata, enabling downstream
consumers to identify which table-extraction algorithm produced a given
table. Version is bumped to `0.22.26` and the changelog is updated
accordingly.
>
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
fe6135af306bc3fb6fbe28db3aa5dc477c4f2ff0. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->
