fix(athena): council review fixes — delegation bug, dead code, test coverage

- Add background_output to council-member allowlist (fixes delegation deadlock)
- Replace empty catch with error logging in prepare-council-prompt
- Remove unnecessary type assertion in agent.ts
- Remove dead hasAgentToolRestrictions function
- Fix incorrect test assertions (undefined vs false semantics)
- Add barrel export for athena module
- Add guard function test coverage (5 tests)
- Add parity test for triple-sync restrictions (9 tests)

src/agents/athena/agent.ts

@@ -238,7 +238,7 @@ export function createAthenaAgent(model: string): AgentConfig {
   // question permission is set by tool-config-handler.ts based on CLI mode (allow/deny)
   const permission = {
     ...restrictions.permission,
-  } as AgentConfig["permission"]
+  }
 
   const base = {
     description:

src/agents/athena/council-member-agent.ts

@@ -52,6 +52,7 @@ export function createCouncilMemberAgent(model: string): AgentConfig {
     "lsp_diagnostics",
     "ast_grep_search",
     "call_omo_agent",
+    "background_output",
   ])
 
   // Explicitly deny TodoWrite/TodoRead even though `*: deny` should catch them.

src/agents/athena/index.ts

@@ -0,0 +1,3 @@
+export { createAthenaAgent, ATHENA_PROMPT_METADATA } from "./agent"
+export { createCouncilMemberAgent, COUNCIL_MEMBER_PROMPT, COUNCIL_DELEGATION_ADDENDUM } from "./council-member-agent"
+export { applyModelThinkingConfig } from "./model-thinking-config"