feat: serve the handheld launchers from the site

build_port's four archives carry install.py pinned by SHA-256, so they
change with the installer, not with the packs. The site now builds them
from its own commit and serves them under get/handheld/. Each get/ page
of Batocera, KNULLI, ROCKNIX and AmberELEC names its file, size, hash,
folder and menu, and get/linux-handhelds/ does the same for muOS, ArkOS,
dArkOS and JELOS. The installer's handheld section opens on a download
table, both tables written from sitehandheld.LAUNCHERS.

scripts/generate_pack.py

@@ -5819,7 +5819,7 @@ def _pack_archives(output_dir: str) -> list[str]:
     fail conformance, and injecting a manifest would change published bytes.
     Every name the builder gives holds `_BIOS_Pack`, then the system tag of
     a --system platform pack (`_BIOS_Pack_Playstation.zip`): build_port.py
-    writes its launcher archives (RetroBIOS.zip) to the same dist/, and
+    wrote its launcher archives (RetroBIOS.zip) to the same dist/, and
     taking every ZIP rewrote them with a manifest after build_port had
     printed their hashes.
     """