Trim over-commented Chunk 3+/4 work

A pass over the install scripts, dev-tools commands, and Hyprland Lua
files that I had stuffed with explain-everything preambles. Most of
those rationales (which files ship where, why hyprctl setenv doesn't
suffice, etc.) belong in commit messages or PR descriptions, not in
code people have to read forever. Kept the few comments that document
genuinely non-obvious behaviour: the keybind-env reason for hl.env in
envs.lua, why the runtime PAM seds stay scripted in
increase-lockout-limit, the chroot/--now distinction in chroot.sh, and
the dev-pkg-test split-install reason.

install/config/mimetypes.sh

@@ -1,10 +1,5 @@
-# Most MIME default mappings now ship as config/mimeapps.list (via /etc/skel
-# for new users; existing users keep their own). This script handles the
-# runtime side: refresh applications, set Chromium as the system default web
-# browser (omarchy-install-browser overrides if the user picks something
-# else later), and wire HEY.desktop as the mailto handler — HEY.desktop is
-# generated by install/packaging/webapps.sh at install time so it can't
-# live in /etc/skel/.config/mimeapps.list.
 omarchy-refresh-applications
 xdg-settings set default-web-browser chromium.desktop
+# HEY.desktop is generated by install/packaging/webapps.sh, so the mapping
+# can't ship as a static /etc/skel/.config/mimeapps.list entry.
 xdg-mime default HEY.desktop x-scheme-handler/mailto