fix(athena): address 11 audit findings (H2,H3,H5,M1-M4,M8-M11)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

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

@@ -1,10 +1,9 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { log, normalizeSDKResponse } from "../../shared"
+import { hasCouncilResponseTag } from "./council-continuation-enforcer"
 
 type OpencodeClient = PluginInput["client"]
 
-const COUNCIL_RESPONSE_TAG = "</COUNCIL_MEMBER_RESPONSE>"
-
 export async function sessionHasCouncilResponse(
   client: OpencodeClient,
   sessionID: string,
@@ -20,18 +19,7 @@ export async function sessionHasCouncilResponse(
       { 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
+    return hasCouncilResponseTag(messages)
   } catch (error) {
     log("[council-response-checker] Error checking session for response tag:", {
       sessionID,