Add DEPENDENCIES.md cataloging project dependencies and svdep status

[Copilot]

Documents all project dependencies managed via IVPM and confirms svdep is not loaded.

Changes

• Added DEPENDENCIES.md: Catalogs 4 dependencies (sphinx, sphinxcontrib-mermaid, myst-parser, zuspec) with sources and purposes
• svdep status: Explicitly documents NOT LOADED—appropriate for this documentation-only project with no SystemVerilog sources
• Usage instructions: IVPM setup and dependency installation commands

Context

Project uses IVPM for dependency management via ivpm.yaml. All current dependencies are documentation tooling (Sphinx ecosystem) plus the core zuspec framework from Git.

Original prompt

Catalog the project dependencies. Check whether svdep is loaded

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