v0.1.8 — fix Gaming Mode 60 Hz launch on NVIDIA + HDMI

Reported by clutchmuffin: TUI saved e.g. CUSTOM_REFRESH_RATES=165 but
Gaming Mode always launched at 60 Hz. Two stacked bugs:

1. Settings TUI wrote ~/.config/environment.d/gamescope-session-plus.conf
   but never reloaded systemd's user env, so the running user manager
   (and therefore gamescope-session-plus@.service) still had the old
   values until next login. Now flush_pending calls
   `systemctl --user import-environment` / `unset-environment` for the
   keys it just touched.

2. CUSTOM_REFRESH_RATES was written as a single scalar. Gamescope's
   --custom-refresh-rates is a list of *switchable* rates, not a
   launch-rate selector — and with no safe 60 Hz fallback in the list,
   some DRM/NVIDIA paths drop to the EDID-preferred 60 Hz on first
   launch. TUI now writes a comma list (e.g. 60,165). show_state and
   confirm_risky_save de-list to the highest member for display /
   validation.

Adds a troubleshooting README entry documenting the Steam BPM
client-side rate persistence as the canonical first-launch workaround.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

bin/deckshift-settings

@@ -109,6 +109,19 @@ flush_pending() {
       echo "${key}=${value}" >> "$CONF"
     fi
   done
+
+  # environment.d/*.conf is parsed by `systemd --user` at user-manager startup,
+  # so edits made here don't reach gamescope-session-plus@.service until the
+  # next login unless we nudge systemd. import-environment pulls the keys we
+  # just wrote into the running user manager scope so the next Gaming Mode
+  # launch sees them without a re-login.
+  if [[ ${#PENDING_SET[@]} -gt 0 ]]; then
+    # shellcheck disable=SC2046
+    systemctl --user import-environment $(printf '%s ' "${!PENDING_SET[@]}") 2>/dev/null || true
+  fi
+  if [[ ${#PENDING_UNSET[@]} -gt 0 ]]; then
+    systemctl --user unset-environment "${!PENDING_UNSET[@]}" 2>/dev/null || true
+  fi
 }
 
 # ------------------------------------------------------------------------------
@@ -225,6 +238,12 @@ show_state() {
   width=$(effective SCREEN_WIDTH)
   height=$(effective SCREEN_HEIGHT)
   refresh=$(effective CUSTOM_REFRESH_RATES)
+  # Stored as a comma list (e.g. "60,165") so gamescope has a safe 60 Hz
+  # fallback. The user only cares about the rate they picked — the highest
+  # member of the list.
+  if [[ "$refresh" == *,* ]]; then
+    refresh=$(tr ',' '\n' <<<"$refresh" | sort -nr | head -1)
+  fi
   vk_adapter=$(effective VULKAN_ADAPTER)
   dri_prime=$(effective DRI_PRIME)
   prime_offload=$(effective __NV_PRIME_RENDER_OFFLOAD)
@@ -385,7 +404,17 @@ choose_refresh_rate() {
     rate=${choice%% *}
   fi
   [[ -z "$rate" ]] && return 0
-  pending_set CUSTOM_REFRESH_RATES "$rate"
+
+  # gamescope-session-plus passes this env value to gamescope as
+  # --custom-refresh-rates, which is a list of *switchable* rates the user can
+  # cycle between in Steam Big Picture. Writing a single value (e.g. "165") can
+  # leave gamescope without a safe 60 Hz fallback if the monitor's EDID
+  # preferred mode is 60 Hz and the high-rate mode isn't enumerated on first
+  # launch — most visibly on NVIDIA HDMI outputs. Always include 60 as the
+  # floor so Steam can fall back and the user can switch up to their pick.
+  local rate_list="$rate"
+  [[ "$rate" != "60" ]] && rate_list="60,${rate}"
+  pending_set CUSTOM_REFRESH_RATES "$rate_list"
 }
 
 # Keys this menu owns. Cleared at the start of every selection so switching
@@ -526,6 +555,11 @@ confirm_risky_save() {
   w=$(effective SCREEN_WIDTH)
   h=$(effective SCREEN_HEIGHT)
   rate=$(effective CUSTOM_REFRESH_RATES)
+  # Check the user's actual pick (highest of the comma list) against monitor
+  # support — not the bare list, which won't match a single mode line.
+  if [[ "$rate" == *,* ]]; then
+    rate=$(tr ',' '\n' <<<"$rate" | sort -nr | head -1)
+  fi
 
   local -a warnings=()
   if [[ -n "$w" && -n "$h" ]] && ! resolution_supported "$w" "$h"; then