fix: bar widget render guard, capability-gated scroll, sidetone rollback

headsetcontrol/widget.luau

@@ -33,6 +33,7 @@ local function batteryColor()
 end
 
 local function render()
+  if not barWidget then return end
   if errorState == "no_binary" then
     barWidget.setGlyph("alert-triangle")
     barWidget.setColor("#e5484d")
@@ -76,8 +77,14 @@ end
 
 local function sendSidetone(value)
   value = math.clamp(value, 0, 128)
+  local previous = sidetoneValue
   hsc.sendCommand({ "-s", tostring(value) }, function(res)
     if res.exitCode ~= 0 then
+      if previous ~= nil then
+        sidetoneValue = previous
+      end
+      sidetoneFlashUntil = 0
+      render()
       noctalia.notifyError(noctalia.tr("error.command_failed"), string.sub(res.stderr or "", 1, 200))
       return
     end
@@ -90,6 +97,7 @@ end
 
 function onScroll(axis, steps)
   if axis ~= "vertical" then return end
+  if not caps.sidetone or errorState ~= "" then return end
   local current = sidetoneValue or noctalia.getConfig("sidetone_default") or 64
   sendSidetone(current + steps * 4)
 end
@@ -126,3 +134,4 @@ noctalia.state.watch("error", function(v) errorState = v or ""; render() end)
 noctalia.state.watch("sidetone", function(v) if v ~= nil then sidetoneValue = v end end)
 
 syncState()
+render()