feat(athena): extract interactive prompt to dedicated file

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

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

src/agents/athena/interactive-prompt.test.ts

@@ -0,0 +1,50 @@
+/// <reference types="bun-types" />
+
+import { describe, expect, it } from "bun:test"
+import { ATHENA_INTERACTIVE_PROMPT } from "./interactive-prompt"
+
+describe("ATHENA_INTERACTIVE_PROMPT", () => {
+  describe("#given the interactive prompt module", () => {
+    describe("#when checking the export", () => {
+      it("#then exports ATHENA_INTERACTIVE_PROMPT as a string", () => {
+        expect(typeof ATHENA_INTERACTIVE_PROMPT).toBe("string")
+      })
+    })
+
+    describe("#when checking structural tags", () => {
+      it("#then contains <identity> tag", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).toContain("<identity>")
+      })
+
+      it("#then contains <workflow> tag", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).toContain("<workflow>")
+      })
+    })
+
+    describe("#when checking interactive-only features", () => {
+      it("#then contains Question tool references", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).toContain("Question tool")
+      })
+
+      it("#then contains switch_agent references", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).toContain("switch_agent")
+      })
+    })
+
+    describe("#when checking workflow steps", () => {
+      it("#then contains Step 1: Route the message", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).toContain("Step 1: Route the message")
+      })
+
+      it("#then contains Step 2: Council setup", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).toContain("Step 2: Council setup")
+      })
+    })
+
+    describe("#when checking non-interactive content exclusion", () => {
+      it("#then does NOT contain <athena_council_result> tag", () => {
+        expect(ATHENA_INTERACTIVE_PROMPT).not.toContain("<athena_council_result>")
+      })
+    })
+  })
+})