fix(post-install): seed stasis config into user home

Stasis ignores /etc/xdg/ and only reads ~/.config/stasis/stasis.rune
(primary) or /etc/stasis/stasis.rune (fallback). On first start with no
user config it writes its own hardcoded default, so Moonarch's tuned
idle plans were never active on fresh installs.

Seed the template from /etc/xdg/stasis/stasis.rune into the user home
before stasis ever starts, only if the user file is missing. See
DECISIONS.md for verification against upstream v1.1.0.

scripts/post-install.sh

@@ -119,6 +119,17 @@ if [[ ! -f "$HOME/.zshrc" ]]; then
     echo "source /etc/zsh/zshrc.moonarch" >> "$HOME/.zshrc"
 fi
 
+# --- Seed Stasis user config ---
+#
+# Stasis reads ~/.config/stasis/stasis.rune (or /etc/stasis/stasis.rune as
+# fallback) but never /etc/xdg/. Without a user config it writes its own
+# upstream default on first start. Seed Moonarch's template so the bootstrap
+# sees an existing file and skips. Never overwrite an existing user config.
+if [[ ! -f "$HOME/.config/stasis/stasis.rune" && -f /etc/xdg/stasis/stasis.rune ]]; then
+    log "Seeding Moonarch stasis config to user home."
+    install -Dm644 /etc/xdg/stasis/stasis.rune "$HOME/.config/stasis/stasis.rune"
+fi
+
 # --- Enable systemd user services ---
 
 log "Enabling systemd user services..."