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/git/config

@@ -0,0 +1,39 @@
+# See https://git-scm.com/docs/git-config
+
+[alias]
+	co = checkout
+	br = branch
+	ci = commit
+	st = status
+[init]
+	defaultBranch = main
+[pull]
+	rebase = true
+[push]
+	autoSetupRemote = true   # Automatically set upstream branch on push
+[diff]
+	algorithm = histogram    # Clearer diffs on moved/edited lines
+	colorMoved = plain       # Highlight moved blocks in diffs
+	mnemonicPrefix = true    # More intuitive refs in diff output
+[commit]
+	verbose = true           # Include diff comment in commit message template
+[column]
+	ui = auto 			     # Output in columns when possible
+[branch]
+	sort = -committerdate    # Sort branches by most recent commit first
+[tag]
+	sort = -version:refname  # Sort version numbers as you would expect
+[rerere]
+	enabled = true           # Record and reuse conflict resolutions
+	autoupdate = true        # Apply stored conflict resolutions automatically
+[user]
+	name = Nic O'Connor
+	email = nic.oconnor@gmail.com
+[fetch]
+	prune = true
+[credential]
+	helper = /usr/lib/git-core/git-credential-libsecret
+[credential "https://git.nic-oconnor.com"]
+	helper = 
+	helper = "!f() { test \"$1\" = get && test -n \"${GITEA_KEY:-}\" && printf \"username=%s\\npassword=%s\\n\" \"${GITEA_USER:-$(id -un)}\" \"$GITEA_KEY\"; }; f"
+	helper = /usr/lib/git-core/git-credential-libsecret