v0.2.1

v0.2.1 - Pizza geometry correction

Corrects a structural error in the Ch3 Pizza Architecture
figure (and the prose around it) that came to light when
the DisComCo 'Cakes, Onions and Pizzas' deck was identified
as the canonical source for the Pizza name and shape.

What changed since v0.2.0:

figs/pizza-architecture.svg fully rewritten:
  - The earlier version drew CMD/PRJ/QRY as three concentric
    rings, which is wrong. CMD/PRJ/QRY are sibling deployables,
    not nested rings.
  - The new version follows the canonical hub-and-spokes
    geometry: Event Store hub, 8 spokes (Desks), each spoke
    containing four colour-coded actor blocks (Emitter,
    Listener, Responder, Requester), Pub/Sub outer ring,
    seven external infrastructure boxes (storage, telemetry,
    hardware, caching, messaging, internet, event stream).

figs/division-company-model.svg added (new Figure 3.2):
  - Sourced from hecate-corpus/assets/cartwheel-company-model.svg
  - Relabeled to library vocabulary throughout
    (capabilities -> loans, HOPE/FACT -> gRPC/Fact,
    Tube Mail -> Event)
  - Shows CMD/PRJ/QRY as three sibling Departments in
    columns, with frontdesks + backoffice desks per
    Department, and tube-mail-style event flow CMD -> PRJ
  - The view that the wheel diagram doesn't easily express

Chapter 3 prose:
  - Section heading 'The three rings: CMD, PRJ, QRY' renamed
    to 'The three Departments: CMD, PRJ, QRY'
  - All three 'X is the Y ring' paragraphs rewritten as
    'X is the Y Department'
  - Figure 3.1 caption rewritten to describe the per-spoke
    actor stack
  - Figure 3.2 inserted with cross-reference @fig-company

Colophon:
  - New acknowledgement crediting DisComCo (discomco.pl)
    for the Pizza Architecture name and the canonical
    hub-and-spokes-with-four-actors diagram

The book now has two correct, complementary illustrations
of a Division's shape: the wheel (Figure 3.1, slicing
emphasis) and the company (Figure 3.2, departmental
emphasis).