feat: Engine diagnostics (#92)

Adds a `Diagnostics` component that shows the following diagnostics from the last realization:

- Confirmation of success or a short description of what failed.
- The value of the loss function at each step.
- The spectrum of the Hessian at each step.

The loss and spectrum plots are shown on switchable panels.

Also includes some refactoring/renaming of existing code.

Co-authored-by: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Reviewed-on: #92
Co-authored-by: Vectornaut <vectornaut@nobody@nowhere.net>
Co-committed-by: Vectornaut <vectornaut@nobody@nowhere.net>

app-proto/run-examples.sh

@@ -0,0 +1,20 @@
+# run all Cargo examples, as described here:
+#
+#   Karol Kuczmarski. "Add examples to your Rust libraries"
+#   http://xion.io/post/code/rust-examples.html
+#
+# you should invoke this script by calling `sh` or another interpreter, rather
+# than calling `souce`, to ensure that the script can find the manifest file for
+# the application prototype
+
+# find the manifest file for the application prototype
+MANIFEST="$(dirname -- $0)/Cargo.toml"
+
+# set up the command that runs each example
+RUN_EXAMPLE="cargo run --manifest-path $MANIFEST --example"
+
+# run the examples
+$RUN_EXAMPLE irisawa-hexlet; echo
+$RUN_EXAMPLE three-spheres; echo
+$RUN_EXAMPLE point-on-sphere; echo
+$RUN_EXAMPLE kaleidocycle