Improve MASM docs discoverability and depth in IA

Source: DevEx Sync (Notion).

MASM reference documentation currently lives under Core Concepts / Protocol but is not intuitive to find for developers writing MASM. Two options were discussed:

1. Stand up a dedicated Miden-flavoured MASM section (e.g. top-level `/masm/` or under Tools), authored in this repo.
2. Update the docs ingestion logic so MASM reference pages from the upstream source are pulled into a more discoverable location with proper sidebar grouping.

Additionally:

- Several MASM pages (and project-template pages) are currently single-page stubs and need deeper content per page rather than one wall.
- Sidebar/IA placement should make the MASM reference reachable in ≤ 2 clicks from the home page.

This issue tracks both the IA decision and the resulting content/ingestion work.

The issue is about the documentation site's information architecture and content. First, examine the repository structure to understand how docs are organized and ingested. Look for sidebar configuration and the location of MASM-related pages. The goal is to make MASM reference documentation more discoverable and expand stub pages, but the specific changes depend on an IA decision not yet made.

Escrito por el modelo de indexación a partir del texto del issue.