interactive: Host/View entry menu, clipboard copy, player picker

Bare `pixelpass` now opens a dialoguer-driven Host/View menu instead of
going straight to host mode. Host path copies the ticket to the system
clipboard via arboard with silent print-only fallback. View path
prompts for the ticket, then after the local listener binds prompts
mpv-vs-VLC and spawns it detached (setsid + null stdio) so the player
survives pixelpass exiting.

Headless invocations (`pixelpass <ticket>`, `pixelpass --repair`)
unchanged. Per spec at ~/Documents/pixelpass-interactive-mode-spec.md.

src/viewer/mod.rs

@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{Context, Result};
 use iroh::Endpoint;
 use iroh::endpoint::presets;
 use iroh_tickets::endpoint::EndpointTicket;
@@ -22,7 +22,17 @@ pub async fn run(ticket: EndpointTicket, opts: ViewerOpts) -> Result<()> {
 
     let listener = TcpListener::bind(("127.0.0.1", opts.port)).await?;
     let port = listener.local_addr()?.port();
-    print_viewer_banner(port);
+    let url = format!("http://127.0.0.1:{port}");
+
+    if opts.interactive {
+        let player = crate::interactive::prompt_player()?;
+        player
+            .spawn(&url)
+            .with_context(|| "failed to launch player")?;
+        print_viewer_banner_interactive();
+    } else {
+        print_viewer_banner(&url);
+    }
 
     let result = tokio::select! {
         accepted = listener.accept() => {
@@ -40,8 +50,7 @@ pub async fn run(ticket: EndpointTicket, opts: ViewerOpts) -> Result<()> {
     result
 }
 
-fn print_viewer_banner(port: u16) {
-    let url = format!("http://127.0.0.1:{port}");
+fn print_viewer_banner(url: &str) {
     eprintln!();
     eprintln!("┌─ PixelPass · viewer ───────────────────────────────────────");
     eprintln!("│  Connected to host. Open the stream in your player:");
@@ -55,3 +64,12 @@ fn print_viewer_banner(port: u16) {
     eprintln!("└────────────────────────────────────────────────────────────");
     eprintln!();
 }
+
+fn print_viewer_banner_interactive() {
+    eprintln!();
+    eprintln!("┌─ PixelPass · viewer ───────────────────────────────────────");
+    eprintln!("│  Player launched. Close it (or press Ctrl+C here) to");
+    eprintln!("│  disconnect.");
+    eprintln!("└────────────────────────────────────────────────────────────");
+    eprintln!();
+}