Add WORKFLOW_DIAGRAM.md with end-to-end RISC-V pipeline Mermaid diagrams

[whensun]

Motivation

• Provide an advisor-friendly, standalone diagram that documents the end-to-end RISC-V pipeline extracted from ALL/ALL.ipynb to make the workflow easier to review and present.
• Give a compact mapping-focused view and practical update instructions so contributors can keep the diagram in sync with changes to notebook stages.

Description

• Add ALL/WORKFLOW_DIAGRAM.md containing a high-level Mermaid flowchart of the pipeline that covers inputs, instruction/register rule synthesis, test-generation/repair, and QEMU/xv6 validation.
• Add a second Mermaid mapping-focused view that shows how specification chunks, metadata extraction, and LLM matching produce rules and feed test generation and validation.
• Include a suggested figure caption for thesis/advisor use and a short update guide that instructs how to regenerate artifacts from ALL/ALL.ipynb and rename Mermaid node labels.
• Include a minimal command checklist with a Python snippet to inspect notebook cells as the source-of-truth for stage ordering.

Testing

• No automated tests were added or run for this documentation-only change.

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Codex Task