Merge installation and first-computation into one Getting started page

The Getting started nav entry landed on a thin hub that only listed two
sub-pages. Fold both into getting-started/index.md so the entry opens a
real page on the first click: an Installation section (uv, pip, legacy
conda) followed by the end-to-end first computation.

The page is now an executable notebook, so drop it from the jupytext
hook's index.md exclusion (it is read via the myst backend, not pandoc)
and exclude getting-started/*.ipynb from Sphinx source collection to
avoid a duplicate-document warning for the paired notebook.

Author: wmayner

.pre-commit-config.yaml

@@ -55,5 +55,5 @@ repos:
         # is absent on CI runners and would crash the hook; excluding the
         # section-hub index.md files keeps the sync to files jupytext can read.
         files: ^docs/(getting-started|tutorials)/.*\.md$
-        exclude: ^docs/(getting-started|tutorials)/index\.md$
+        exclude: ^docs/tutorials/index\.md$
         require_serial: true

docs/conf.py

@@ -30,9 +30,9 @@
     "superpowers/**",
     "**/.ipynb_checkpoints",
     "examples/IIT_4.0_demo.ipynb",
-    "getting-started/first-computation.ipynb",
-    # Paired tutorial notebooks are download artifacts; the .md is the rendered
-    # source. Exclude the .ipynb so Sphinx does not see two files per document.
+    # Paired notebooks are download artifacts; the .md is the rendered source.
+    # Exclude the .ipynb so Sphinx does not see two files per document.
+    "getting-started/*.ipynb",
     "tutorials/*.ipynb",
 ]