feat(cli): remove --mic (microphone is out of scope)

pixelpass is a screen-share tool meant to be paired with a dedicated
voice app (Mumble, TeamSpeak, Discord, …) for two-way talk — it never
mixes a mic. The --mic flag was declared, shown in the host banner, and
documented as working, but was never wired into the gst pipeline (a
no-op). Removed the flag from Cli + HostOpts + into_host_opts, dropped
it from the banner capture summary, and replaced the README's "--mic
mixes the mic" claim with an explicit out-of-scope note.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/cli.rs

@@ -21,10 +21,6 @@ pub struct Cli {
     #[arg(long, value_name = "NAME")]
     pub app: Option<String>,
 
-    /// Mix in the default microphone source.
-    #[arg(long)]
-    pub mic: bool,
-
     /// Override display server autodetection.
     #[arg(long, value_enum)]
     pub display_server: Option<DisplayServerArg>,
@@ -79,7 +75,6 @@ pub enum DisplayServerArg {
 pub struct HostOpts {
     pub window: bool,
     pub app: Option<String>,
-    pub mic: bool,
     pub display_server: Option<DisplayServerArg>,
     pub bitrate: u32,
     pub framerate: u32,
@@ -99,7 +94,6 @@ impl Cli {
         HostOpts {
             window: self.window,
             app: self.app,
-            mic: self.mic,
             display_server: self.display_server,
             bitrate: self.bitrate,
             framerate: self.framerate,

src/host/mod.rs

@@ -342,8 +342,5 @@ fn capture_summary(opts: &HostOpts) -> String {
     } else {
         bits.push("system-audio".to_string());
     }
-    if opts.mic {
-        bits.push("mic".to_string());
-    }
     bits.join(" + ")
 }