Rework Makefile with install/link/update targets and auto-generation

Add gen-update-targets.sh to parse flake.nix and generate grouped
update targets (update-kyle, update-mc). Makefile now has install
(copy) and link (symlink) targets for rebuild-nixos. Also fix mc
flake input URLs to use /mc/ org path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

script/gen-update-targets.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+declare -A groups
+
+while IFS= read -r line; do
+	# skip comments
+	[[ $line =~ ^[[:space:]]*# ]] && continue
+
+	if [[ $line =~ ^[[:space:]]*([a-zA-Z0-9_-]+)\.url[[:space:]]*=[[:space:]]*\"(.+)\"\; ]]; then
+		name="${BASH_REMATCH[1]}"
+		url="${BASH_REMATCH[2]}"
+
+		if [[ $url =~ wntrmute\.dev/kyle/ ]] || [[ $url =~ github:kisom/ ]]; then
+			groups[kyle]+="${groups[kyle]:+ }$name"
+		elif [[ $url =~ wntrmute\.dev/mc/ ]]; then
+			groups[mc]+="${groups[mc]:+ }$name"
+		fi
+	fi
+done < flake.nix
+
+phony=""
+targets=""
+
+for group in $(printf '%s\n' "${!groups[@]}" | sort); do
+	inputs="${groups[$group]}"
+	if [[ -n "$inputs" ]]; then
+		phony+=" update-$group"
+		targets+="update-${group}:"$'\n\t'"nix flake update ${inputs}"$'\n\n'
+	fi
+done
+
+printf '.PHONY:%s\n\n%s' "$phony" "$targets"