feat(plugins): complete Campaign LA5 cross-host hosting

src/AcDream.Runtime/Session/SessionStatusWriter.cs

@@ -13,9 +13,9 @@ namespace AcDream.Runtime.Session;
 /// is a single shared-stdout JSONL diagnostics stream with no per-session
 /// file; this class writes one file per session, meant to be read by an
 /// external process (the launcher) rather than scraped from console output.
-/// Event shapes are versioned (<c>"v":1</c>) so a future event kind
-/// (<c>pluginLoaded</c>/<c>pluginFailed</c>, LA5) can be added without
-/// breaking an existing reader.
+/// Event shapes are versioned (<c>"v":1</c>); LA5's
+/// <c>pluginLoaded</c>/<c>pluginFailed</c> additions use that same envelope
+/// without breaking an existing reader.
 /// </para>
 ///
 /// <para>
@@ -29,9 +29,11 @@ namespace AcDream.Runtime.Session;
 /// </para>
 ///
 /// <para>
-/// <strong>Never write credential material into this stream.</strong> Every
-/// event method below takes only identifiers, names, and counts — there is no
-/// parameter shape that could carry a password, by construction.
+/// <strong>Never write credential material into this stream.</strong> LA5's
+/// <see cref="PluginFailed"/> diagnostic is caller-supplied text, so hosts may
+/// pass only the plugin lifecycle failure and must never append session
+/// credentials or other secrets. Neither plugin host exposes credentials
+/// through <c>IPluginHost</c>.
 /// </para>
 ///
 /// <para>
@@ -205,6 +207,27 @@ public sealed class SessionStatusWriter
             characterName,
         });
 
+    public void PluginLoaded(string sessionId, string plugin) =>
+        Write(new
+        {
+            v = VocabularyVersion,
+            e = "pluginLoaded",
+            t = Now(),
+            sessionId,
+            plugin,
+        });
+
+    public void PluginFailed(string sessionId, string plugin, string error) =>
+        Write(new
+        {
+            v = VocabularyVersion,
+            e = "pluginFailed",
+            t = Now(),
+            sessionId,
+            plugin,
+            error,
+        });
+
     public void Disconnected(string sessionId, string reason)
     {
         if (!IsEnabled)