TASK 5 items 1-3: reusable stream, health banner, docs refresh

- Reusable stream: GetOrCreateReusableStreamAsync, cached via LayoutStore, bound at broadcast insert
- Health monitoring: GetStreamHealthAsync polls liveStreams.status, report-by-exception banner
- Go-live order: ensure stream → create broadcast → then start pump (URL must exist first)
- Full broadcast form scoped (TASK 5 items 6-7) in TASKS.md + ai.md
- TASK 23 trimmed to technical scope, TASK 26 added (marcom/launch kit)
- Confidential files: MONETIZATION.md + MARCOM.md (gitignored, not committed)
- .gitignore updated for confidential business files
- HANDOFF.md updated with session state and next steps

Models/StreamConfig.cs

@@ -29,7 +29,24 @@ public class StreamHealth
     public TimeSpan StreamDuration { get; set; }
     public string? LastError { get; set; }
 
-    // YouTube-specific
-    public string? HealthStatus { get; set; }  // "good", "bad", "ok"
+    // YouTube-specific (liveStreams.status)
+    public string? HealthStatus { get; set; }  // "good", "ok", "bad", "noData"
     public string? HealthMessage { get; set; }
+
+    // Report-by-exception (TASK 5 item 3): configurationIssues[] — the banner
+    // surfaces only warning/error entries.
+    public List<StreamConfigurationIssue> ConfigurationIssues { get; } = new();
+}
+
+public enum StreamIssueSeverity
+{
+    Info,
+    Warning,
+    Error
+}
+
+public class StreamConfigurationIssue
+{
+    public StreamIssueSeverity Severity { get; set; }
+    public string? Type { get; set; }
 }