Fix overlay _air: probesize su intake RTMP e rilevamento zombie

Senza analyzeduration/probesize l'overlay non pubblicava su _air;
YouTube restava in attesa. Esclusi processi ffmpeg zombie da running?.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/models/stream_event.rb

@@ -1,7 +1,7 @@
 class StreamEvent < ApplicationRecord
   EVENT_TYPES = %w[
     connected disconnected reconnected quality_changed error paused resumed
-    started ended network_test pairing
+    started ended network_test pairing youtube_ready
   ].freeze
 
   belongs_to :stream_session

backend/app/services/streams/overlay_relay.rb

@@ -30,6 +30,7 @@ module Streams
         ffmpeg_pid = Process.spawn(
           "ffmpeg", "-nostdin", "-hide_banner", "-loglevel", "warning",
           "-fflags", "+genpts+discardcorrupt",
+          "-analyzeduration", "10000000", "-probesize", "10000000",
           "-rw_timeout", "15000000",
           "-i", intake,
           "-f", "image2pipe", "-framerate", overlay_fps.to_s, "-i", pipe.to_s,
@@ -193,9 +194,12 @@ module Streams
       end
 
       def process_alive?(pid)
+        stat = File.read("/proc/#{pid.to_i}/stat")
+        return false if stat.split[2] == "Z"
+
         Process.kill(0, pid.to_i)
         true
-      rescue Errno::ESRCH, Errno::EPERM
+      rescue Errno::ESRCH, Errno::EPERM, Errno::ENOENT
         false
       end
 

backend/app/services/streams/youtube_relay.rb

@@ -129,9 +129,12 @@ module Streams
       end
 
       def process_alive?(pid)
+        stat = File.read("/proc/#{pid.to_i}/stat")
+        return false if stat.split[2] == "Z"
+
         Process.kill(0, pid.to_i)
         true
-      rescue Errno::ESRCH, Errno::EPERM
+      rescue Errno::ESRCH, Errno::EPERM, Errno::ENOENT
         false
       end