Capture omarchy-air's customizations as a per-host overlay

hosts/<hostname>/{config,system}/ now overlays the shared trees. install.sh
installs a host file in place of the shared copy at the same path, and
capture.sh pulls back into whichever copy the host installs from. That keeps
hardware-specific files off the wrong machine: the HP's EDID-named monitors.lua
and its fnmode=2 would otherwise land on the Air.

capture.sh refreshes the shared trees only on omarchy-laptop, where they were
captured, or when CAPTURE_SHARED=1 is set. On the Air, a plain run copied its
stock terminal, hypr and shell files over every one of the HP's customizations.

air's overlay holds monitors.lua (1.33333 scale and GDK_SCALE=1 for the
2560x1664 panel), input.lua (stock settings plus the inert-accel measurements),
herdr onboarding=false, git identity and credential helpers (no secrets),
mimeapps.list, and the Asahi installer's hid_apple fnmode=1 and show_notch=1.
bindings.lua is not overlaid because the shared one is a strict superset.
hosts/omarchy-air/README.md records what was left out on purpose and why, and
warns that the shared packages.txt is x86-specific.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KKPyqMc7MGKyBLKVdeDejp

hosts/omarchy-air/config/mimeapps.list

@@ -0,0 +1,26 @@
+
+[Default Applications]
+text/plain=nvim.desktop
+text/english=nvim.desktop
+text/x-makefile=nvim.desktop
+text/x-c++hdr=nvim.desktop
+text/x-c++src=nvim.desktop
+text/x-chdr=nvim.desktop
+text/x-csrc=nvim.desktop
+text/x-java=nvim.desktop
+text/x-moc=nvim.desktop
+text/x-pascal=nvim.desktop
+text/x-tcl=nvim.desktop
+text/x-tex=nvim.desktop
+application/x-shellscript=nvim.desktop
+text/x-c=nvim.desktop
+text/x-c++=nvim.desktop
+application/xml=nvim.desktop
+text/xml=nvim.desktop
+text/html=chromium.desktop
+x-scheme-handler/http=chromium.desktop
+x-scheme-handler/https=chromium.desktop
+x-scheme-handler/about=chromium.desktop
+x-scheme-handler/unknown=chromium.desktop
+x-scheme-handler/mailto=HEY.desktop
+x-scheme-handler/claude-cli=claude-code-url-handler.desktop