Consolidate sequence diagrams into the top-level wool README

[conradbzura]

Summary

Remove the Mermaid sequence diagrams from the four subpackage READMEs under wool/src/wool/runtime/ and create a single comprehensive sequence diagram in the top-level wool/README.md.

The subpackage READMEs that currently contain sequence diagrams:

• wool/src/wool/runtime/worker/README.md — Worker execution sequence
• wool/src/wool/runtime/loadbalancer/README.md — Load balancing sequence
• wool/src/wool/runtime/routine/README.md — Routine dispatch sequence
• wool/src/wool/runtime/discovery/README.md — Discovery sequence

Motivation

The individual diagrams each document one layer of the runtime in isolation. A single consolidated diagram in the top-level README gives readers a complete picture of Wool's distributed task execution flow — from routine invocation through discovery, load balancing, worker dispatch, and result return — without having to navigate into subpackage directories and mentally stitch the pieces together.

Affected code

• wool/README.md
• wool/src/wool/runtime/worker/README.md
• wool/src/wool/runtime/loadbalancer/README.md
• wool/src/wool/runtime/routine/README.md
• wool/src/wool/runtime/discovery/README.md