fix(hyprlua): flatten presence-detect's check cycle to 20s

Replace the three-tier load-adaptive polling (20s/120s/600s based on CPU-or-
RAM usage) with a flat 20s interval — fido2-token -L is cheap enough that
backing off under load isn't worth the added complexity or the latency in
noticing a key was removed.

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

desktopenvs/hyprlua/scripts/presence-detect.sh

@@ -1,9 +1,8 @@
 #!/bin/bash
 # FIDO key presence detection daemon.
-# Checks whether a FIDO2/U2F security key is plugged in, at an adaptive
-# interval (20s under light load, 120s under moderate load, 600s under heavy
-# load), and shares caffeine's systemd-inhibit idle lock while a key is
-# present, so hypridle never fires during an active session.
+# Checks whether a FIDO2/U2F security key is plugged in, every 20s flat, and
+# shares caffeine's systemd-inhibit idle lock while a key is present, so
+# hypridle never fires during an active session.
 #
 # Detection: `fido2-token -L` (libfido2) enumerates connected FIDO CTAP
 # devices by USB HID usage page — no touch/tap required, so this is a pure
@@ -25,12 +24,7 @@ OWNED_FLAG="/tmp/presence-inhibit-owned"
 # stays live even then — only the inhibit ownership differs.
 PRESENCE_FLAG="/tmp/presence-detected"
 
-INTERVAL_LIGHT=20    # seconds between checks when CPU-or-RAM usage < LOAD_LIGHT
-INTERVAL_MID=120     # seconds between checks when usage is between the two thresholds
-INTERVAL_HEAVY=600   # seconds between checks when usage >= LOAD_HEAVY
-LOAD_LIGHT=0.20       # CPU-or-RAM fraction below which we poll at INTERVAL_LIGHT
-LOAD_HEAVY=0.50       # CPU-or-RAM fraction at/above which we back off to INTERVAL_HEAVY
-NPROC="$(nproc)"
+INTERVAL=20   # seconds between checks, flat regardless of system load
 
 # True if any FIDO2/U2F authenticator is currently enumerable over USB.
 # fido2-token -L lists one line per connected device and needs no PIN, touch,
@@ -39,29 +33,6 @@ _fido_key_present() {
     [[ -n "$(fido2-token -L 2>/dev/null)" ]]
 }
 
-# Prints current CPU-or-RAM usage as a fraction (0..1): the higher of the
-# core-count-normalized 1-minute load average and the used-RAM fraction. Load
-# average is a cheap, sampling-free proxy for "CPU busy" — no extra measurement
-# delay per tick.
-_resource_usage() {
-    local load1 cpu_frac mem_frac
-    load1="$(awk '{print $1}' /proc/loadavg)"
-    cpu_frac="$(awk -v l="$load1" -v n="$NPROC" 'BEGIN{print l/n}')"
-    mem_frac="$(free | awk '/^Mem:/ {print $3/$2}')"
-    awk -v c="$cpu_frac" -v m="$mem_frac" 'BEGIN{print (c>m)?c:m}'
-}
-
-# Three-tier poll interval based on current resource usage:
-#   >= LOAD_HEAVY  -> INTERVAL_HEAVY (heavy load: back off, stay out of the way)
-#   <  LOAD_LIGHT  -> INTERVAL_LIGHT (near-idle: poll fast, cheap and responsive)
-#   otherwise      -> INTERVAL_MID   (moderate load)
-_next_interval() {
-    local u; u="$(_resource_usage)"
-    awk -v u="$u" -v heavy="$LOAD_HEAVY" -v light="$LOAD_LIGHT" \
-        -v fh="$INTERVAL_HEAVY" -v fl="$INTERVAL_LIGHT" -v fm="$INTERVAL_MID" \
-        'BEGIN{ if (u >= heavy) print fh; else if (u < light) print fl; else print fm }'
-}
-
 # Returns true if the inhibitor sentinel process is still alive.
 _inhibit_running() {
     [[ -f "$PID_FILE" ]] && kill -0 "$(cat "$PID_FILE")" 2>/dev/null
@@ -122,5 +93,5 @@ while true; do
         _stop_inhibit
     fi
 
-    sleep "$(_next_interval)"
+    sleep "$INTERVAL"
 done