Increase side padding on code blocks

Code text sat too close to the panel border. Bump horizontal padding from
1.2em to 1.5em on highlighted blocks, add the same padding to bare
pre>code blocks (previously only bordered), and align the fence title bar
to 1.5em so the filename lines up with the code text.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Netdocs

src/Netdocs.Theme.Material/assets/netdocs.css

@@ -197,13 +197,14 @@ body {
 /* Give code content a little more horizontal breathing room so text is never
    flush against the panel border. */
 .md-typeset .highlight > pre > code {
-  padding: 0.75em 1.2em;
+  padding: 0.8em 1.5em;
 }
 
 /* Bare <pre><code> blocks (not wrapped in a .highlight container) still need a
    panel border, but a wrapped block must NOT get a second, inset border on the
    inner <code> — that produced the "double border" seen on the reference page. */
 .md-typeset pre > code {
+  padding: 0.8em 1.5em;
   border: 0.05rem solid var(--md-default-fg-color--lightest);
   border-radius: 0.2rem;
   box-shadow: var(--nd-code-shadow);
@@ -235,7 +236,7 @@ body {
   margin: 0;
   font-size: 0.85em;
   font-weight: 700;
-  padding: 0.5em 1em;
+  padding: 0.5em 1.5em;
   border-top-left-radius: 0.2rem;
   border-top-right-radius: 0.2rem;
   background: color-mix(in srgb, var(--md-code-bg-color) 100%, var(--md-default-fg-color) 6%);