docs+install: post-rename docs polish, install script, d2 architecture diagram (#26)

* docs: add sanderling bird artwork to README and docs index

* chore: add one-line install script for macOS and Linux

Detects os/arch, resolves latest (or pre-)release, verifies sha256,
and installs the binary into $HOME/.sanderling/bin.

* docs: use the one-line installer in getting-started

Replaces the broken `<version>` placeholder snippets with the
install.sh one-liner.

* docs: drop filler line under the install one-liner

* docs: rename index heading to Sanderling Manual

* docs(style): adopt JetBrains Mono and uppercase brand mark

* docs(getting-started): use justfile flow for folio sample

* docs(writing-specs): drop 'coming soon' notes for eventually and implies

* docs(inspect): rewrite layout for tabbed state panels and metrics chart

* docs(inspect): add UI screenshot

* docs: add Inspect to sidebar and index

* docs: restore mermaid bootstrap script in page template

* docs(style): constrain article images to content width

* docs(inspect): drop layout prose, keep what the screenshot doesn't show

* docs(architecture): add d2 source for architecture diagram

Replaces the in-page mermaid block with a d2-rendered SVG. Generated
outputs (svg/png) stay out of git; only the .d2 source is checked in.

* build(docs): render d2 diagrams into build/site/_assets/diagrams

* docs(architecture): swap mermaid block for rendered d2 svg

* ci(docs): install d2 before building the site

* docs(architecture): tighten layout and reroute label-crossing edges

Flip device/sidecar order so trace writer drops cleanly to runs/
without cutting through the JVM cell, right-align the inspect row
via a pad column, and tune grid gaps to keep gRPC and Unix socket
labels off the SANDERLING boundary.

README.md

@@ -13,3 +13,9 @@ Autonomous property-based testing for mobile apps. Specs in TypeScript. Core in
 - [Architecture](https://priyanshujain.github.io/sanderling/development/architecture.html)
 
 After a `sanderling test` run, browse traces locally with `sanderling inspect`. It opens a web UI for stepping through actions, screenshots, snapshots, residual formulas, and exceptions.
+
+---
+
+<img src="docs/_assets/sanderling.jpeg" alt="sanderling" width="420" />
+
+> sanderling, a wading bird that probes the shoreline for bugs that lie beneath.