[Docs] Consolidate root-level markdown sprawl into a single documentation entry point (#243)

[modrispath]

Closes #243

Summary of Changes

• Created centralized documentation hub at /docs/README.md organized into 4 audience goals: 'run locally', 'add a translation', 'understand the architecture', and 'write a WASM parser'.
• Moved 19 one-off historical PR summaries and deliverable reports from root into /docs/archive/ marked as historical project artifacts.
• Added prominent banner in README.md pointing to /docs/README.md.
• Added explicit cross-referencing between ARCHITECTURE.md and MICROSERVICES_ARCHITECTURE.md.
• Verified registry schema validation passes cleanly.