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/plugin/tool-registry.ts

@@ -281,7 +281,7 @@ export function createToolRegistry(args: {
     ...taskToolsRecord,
     ...hashlineToolsRecord,
     prepare_council_prompt: createPrepareCouncilPromptTool(ctx.directory),
-    council_finalize: createCouncilFinalize(),
+    council_finalize: createCouncilFinalize(ctx.directory),
     council_read: createCouncilRead(),
   }