feat(chezmoi): add gating skeleton — config template, templated ignore, packages manifest

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.chezmoiignore.tmpl

@@ -0,0 +1,27 @@
+# Repo docs — never applied to $HOME
+MIGRATION-NOTES.md
+README.md
+
+# Runtime/plugin state living inside managed trees — not managed
+.config/lazygit/.omc/**
+.config/yazi/plugins/**
+.config/yazi/flavors/**
+.config/tmux/plugins/**
+.config/fish/fish_variables
+.config/nvim/lazy-lock.json
+
+{{ if ne .chezmoi.os "linux" }}
+# Arch desktop layer — linux only
+.config/niri
+.config/niri/**
+.config/noctalia
+.config/noctalia/**
+.config/niri-dynamic-workspaces
+.config/niri-dynamic-workspaces/**
+.config/fontconfig
+.config/fontconfig/**
+.config/mimeapps.list
+.config/systemd
+.config/systemd/**
+.local/bin/niri-launch
+{{ end }}