docs: allow long links to wrap per character to prevent page overflow

Some documentation pages contain long link text without natural
break points, which can force page-wide horizontal scroll overflow
on small screens.

Use overflow-wrap: anywhere for anchor text in the docs stylesheet so
links can wrap per character as a fallback when normal word boundaries
are unavailable.

Examples:
  https://docs.kernel.org/6.15/firmware-guide/acpi/non-d0-probe.html
  https://docs.kernel.org/6.15/arch/x86/earlyprintk.html

Signed-off-by: Rito Rhymes <rito@ritovision.com>
Assisted-by: Codex:GPT-5.4
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260323152428.30483-1-rito@ritovision.com>

Documentation/sphinx-static/custom.css

@@ -170,6 +170,11 @@ div.body table.docutils a.reference {
     overflow-wrap: anywhere;
 }
 
+/* Let long link text wrap instead of forcing overflow. */
+a {
+    overflow-wrap: anywhere;
+}
+
 /* Make xrefs more universally visible */
 a.reference, a.reference:hover {
     border-bottom: none;