amacgregor / amgr_phx / 5858f7e9d21ae345a288bb7f8491807304f3dce6-PR-72

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Pull #72

github

Add concept simulations: a deterministic sim engine, 25 scenes and a lab

Interactive animations of systems concepts, embeddable in articles with a
```viz fence and tuned in a dev-only workbench at /lab.

The engine is a seeded discrete-event queueing simulator on a fixed 8ms
timestep, decoupled from rAF so a run is reproducible from its seed. Node
vocabulary: source, queue, pool, sink, mirror, router, limiter, batcher,
resource and gate. `resource` is the one worth naming — a permit held across
stages, which is what a row lock actually is and what no arrangement of
servers can express.

Rendering is SVG through a retained keyed element pool. Nine scenes carry
their own spatial grammar rather than the generic left-to-right conveyor,
because the conveyor answers "where does the work go" and most of these
concepts aren't about that: a timeline for poll intervals, a log-time axis
for backoff, occupancy for head-of-line blocking, convergence for lock
contention, descent and scatter for index access, pulse for batching. Three
scenes stay conveyors because they genuinely are queueing systems.

Everything drawn is a token in a real state. Readouts carry an optional
numeric channel that draws ~14s of history under the number, which matters
because every metric is a windowed EWMA and one read seconds after a change
can sit above a ceiling it cannot exceed.

Scenes declare `actions:` so the reader causes the event rather than waiting
for it — send a burst, send a slow request, one slow transaction.

Numeric claims are checked against closed forms rather than eyeballed:
ETS 500/s against 6/0.012, GenServer 83.3/s against 1000/12, a p99 of 280ms
against 24 readers x 12ms, Little's Law residual within 1-12%.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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