feat(athena): council member continuation enforcer, tool allowlist, and prompt fixes

- Add council-continuation-enforcer to nudge council members until they
  output COUNCIL_MEMBER_RESPONSE, replacing the hacky post-compaction hack
- Add background_wait + background_cancel to council member tool allowlist
  so members can properly manage their explore agents before responding
- Update COUNCIL_DELEGATION_ADDENDUM prompt to instruct members to cancel
  pending tasks and wait for explore results before final response
- Fix council_finalize path resolution to use project directory
- Remove post-compaction-continuation.ts and recentlyCompactedSessions hack
- Add council-response-checker for detecting response tag in session messages

src/features/background-agent/council-response-checker.ts

@@ -0,0 +1,42 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import { log, normalizeSDKResponse } from "../../shared"
+
+type OpencodeClient = PluginInput["client"]
+
+const COUNCIL_RESPONSE_TAG = "</COUNCIL_MEMBER_RESPONSE>"
+
+export async function sessionHasCouncilResponse(
+  client: OpencodeClient,
+  sessionID: string,
+): Promise<boolean> {
+  try {
+    const response = await client.session.messages({
+      path: { id: sessionID },
+    })
+
+    const messages = normalizeSDKResponse(
+      response,
+      [] as Array<{ info?: { role?: string }; parts?: Array<{ type?: string; text?: string }> }>,
+      { preferResponseOnMissingData: true },
+    )
+
+    for (let i = messages.length - 1; i >= 0; i--) {
+      const msg = messages[i]
+      if (msg.info?.role !== "assistant") continue
+      const parts = msg.parts ?? []
+      for (const part of parts) {
+        if (part.type === "text" && part.text?.includes(COUNCIL_RESPONSE_TAG)) {
+          return true
+        }
+      }
+    }
+
+    return false
+  } catch (error) {
+    log("[council-response-checker] Error checking session for response tag:", {
+      sessionID,
+      error: String(error),
+    })
+    return false
+  }
+}