refactor(athena): delete athena_council tool directory

Remove the entire custom tool implementation (constants, launcher, session-waiter, tool-helpers, tools, types, and all tests). Council members are now launched via the standard task tool.

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

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

src/tools/athena-council/council-launcher.ts

@@ -1,18 +0,0 @@
-import type { CouncilLauncher, CouncilLaunchInput } from "../../agents/athena/council-orchestrator"
-import type { BackgroundManager } from "../../features/background-agent"
-
-export function createCouncilLauncher(manager: BackgroundManager): CouncilLauncher {
-  return {
-    launch(input: CouncilLaunchInput) {
-      return manager.launch({
-        description: input.description,
-        prompt: input.prompt,
-        agent: input.agent,
-        parentSessionID: input.parentSessionID,
-        parentMessageID: input.parentMessageID,
-        parentAgent: input.parentAgent,
-        model: input.model,
-      })
-    },
-  }
-}