feat(calls): 'You're muted' nudge when talking into a muted mic (#117)

Host half of the talking-while-muted feature. The fork (0.25.0-lotus.9)
reports speakingWhileMuted for the local participant in io.lotus.call_state —
a level tap on the muted track, so cinny captures no audio. useMutedTalkWarning
polls that flag while muted; after 1.5 s of it being true it shows one sticky
toast, "You're muted — click to unmute", whose click unmutes; it fires at most
once per mute session (re-arms after unmute → mute), is retired the moment the
mic comes back on by any means, and never runs in Push-to-Talk mode. Setting
'Warn me when I talk while muted' (default on) sits next to AFK Auto-Mute.

Verified headless with a tone mic: no toast at +1 s, toast at +4 s, click
unmutes and clears it, second mute re-arms, unmute via the button clears it,
PTT mode → nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/settings/general/General.tsx

@@ -1648,6 +1648,7 @@ function Calls() {
   const [deafenHotkey, setDeafenHotkey] = useSetting(settingsAtom, 'deafenHotkey');
   const [globalCallHotkeys, setGlobalCallHotkeys] = useSetting(settingsAtom, 'globalCallHotkeys');
   const [afkAutoMute, setAfkAutoMute] = useSetting(settingsAtom, 'afkAutoMute');
+  const [mutedTalkWarning, setMutedTalkWarning] = useSetting(settingsAtom, 'mutedTalkWarning');
   const [afkTimeoutMinutes, setAfkTimeoutMinutes] = useSetting(settingsAtom, 'afkTimeoutMinutes');
   const [callJoinLeaveSound, setCallJoinLeaveSound] = useSetting(
     settingsAtom,
@@ -2012,6 +2013,13 @@ function Calls() {
         direction="Column"
         gap="400"
       >
+        <SettingTile
+          title="Warn me when I talk while muted"
+          description="Shows a one-time 'You're muted' nudge with an Unmute button when the mic hears you but is muted. Never while Push to Talk is on."
+          after={
+            <Switch variant="Primary" value={mutedTalkWarning} onChange={setMutedTalkWarning} />
+          }
+        />
         <SettingTile
           title="AFK Auto-Mute"
           description="Automatically mute your microphone when you have been silent in a call."