fix(session-registry): drop custom taskKey from sessions.create to avoid upstream contract mismatch

Removes `taskKey: discord-thread-${threadId}` from the
`ctx.agents.sessions.create()` call in `spawnAgentInThread`. PaperClip's
plugin-host honors arbitrary taskKey values at create time, but every
subsequent SDK op (sendMessage/list/close) filters sessions by
`taskKey LIKE 'plugin:${pluginKey}:session:%'`. Custom keys orphan the
session — sendMessage immediately throws `Session not found`, falling
through to the ACP fallback which has no consumer in default installs.

The custom taskKey was decorative (grepped — never read elsewhere in
the plugin). Dropping it lets the host generate the prefixed default
form so downstream ops succeed.

Fixes #49. Related: paperclipai/paperclip#6156 (upstream root cause).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mrobinson2

src/session-registry.ts

@@ -274,8 +274,8 @@ export async function spawnAgentInThread(
   let transport: TransportKind = "native";
 
   try {
+    // Do not pass a custom `taskKey` — host's sendMessage/list/close filter on `plugin:${pluginKey}:session:%`, so any user-supplied key becomes invisible to subsequent SDK calls.
     const session = await ctx.agents.sessions.create(agentId, companyId, {
-      taskKey: `discord-thread-${threadId}`,
       reason: `Spawned in Discord thread for: ${taskPrompt.slice(0, 200)}`,
     });
     sessionId = session.sessionId;