refactor: improve robustness and consistency across all scripts

- kb-blackout: optimize trim(), fix log units, add jit fallback
- ac-power: extract error handling helper, add capture_stderr,
  validate timeout, add security note, rename CONFIG to config
- touch-gestures: add min_brightness config, optimize brightnessctl
  to single call, improve wpctl regex, add shutdown handler

scripts/kb-blackout.lua

@@ -30,7 +30,7 @@ local config = {
 local mp = require("mp")
 local msg = require("mp.msg")
 local utils = require("mp.utils")
-local jit = rawget(_G, "jit")
+local jit = rawget(_G, "jit") or {}
 
 local function coerce_boolean(value, default)
   if type(value) == "boolean" then
@@ -137,7 +137,7 @@ if unsupported_platform() then
 end
 
 local function trim(str)
-  return (str and str:gsub("^%s+", ""):gsub("%s+$", "")) or ""
+  return str and str:match("^%s*(.-)%s*$") or ""
 end
 
 local function build_brightnessctl_args(extra)
@@ -315,8 +315,9 @@ end
 
 local function schedule_timer()
   cancel_timer()
-  state.timer = mp.add_timeout(seconds(config.timeout_ms), arm_disable_callback)
-  msg.verbose(("Inactivity timer armed for %.0f ms"):format(config.timeout_ms))
+  local delay = seconds(config.timeout_ms)
+  state.timer = mp.add_timeout(delay, arm_disable_callback)
+  msg.verbose(("Inactivity timer armed for %.1f s"):format(delay))
 end
 
 local function restore_backlight(reason)