refactor(runtime): remove dead prompt test helpers

- Drop deprecated no-op prompt cache testing exports

- Remove the stale test that only exercised those helpers

Co-Authored-By: devagent <devagent@egavrin>

Author: egavrin

packages/runtime/src/engine/agent-prompt.test.ts

@@ -4,8 +4,6 @@ import { join } from "node:path";
 import { afterEach, expect, it } from "vitest";
 
 import {
-  __getCommonPromptReadCountForTesting,
-  __resetCommonPromptCacheForTesting,
   assembleAgentSystemPrompt,
   clearPromptCache,
 } from "./agent-prompt.js";
@@ -113,29 +111,6 @@ it("preserves strong delegation rules in the role prompt when provided", () => {
   expect(prompt).toContain("Delegation is required when task instructions explicitly require it.");
 });
 
-it("caches the shared common prompt across prompt assemblies", () => {
-  repoRoot = join(tmpdir(), `devagent-agent-prompt-${Date.now()}-cache`);
-  mkdirSync(repoRoot, { recursive: true });
-  __resetCommonPromptCacheForTesting();
-
-  assembleAgentSystemPrompt({
-    agentType: AgentType.EXPLORE,
-    repoRoot,
-    rolePrompt: "You are an Explore agent.",
-    availableTools: readonlyTools,
-  });
-  assembleAgentSystemPrompt({
-    agentType: AgentType.REVIEWER,
-    repoRoot,
-    rolePrompt: "You are a Reviewer agent.",
-    availableTools: readonlyTools,
-  });
-
-  // Prompts are now embedded constants — read count is always 0
-  expect(__getCommonPromptReadCountForTesting()).toBe(0);
-  __resetCommonPromptCacheForTesting();
-});
-
 it("omits delegation guidance when the child does not actually have delegate", () => {
   repoRoot = join(tmpdir(), `devagent-agent-prompt-${Date.now()}-general`);
   mkdirSync(repoRoot, { recursive: true });

packages/runtime/src/engine/agent-prompt.ts

@@ -273,16 +273,6 @@ export function loadAgentProjectInstructions(repoRoot: string): string | null {
     .join("\n\n");
 }
 
-/** @deprecated Prompts are now embedded constants — cache reset is a no-op. */
-export function __resetCommonPromptCacheForTesting(): void {
-  // No-op: prompts are embedded constants, no filesystem cache to reset.
-}
-
-/** @deprecated Prompts are now embedded constants — always returns 0. */
-export function __getCommonPromptReadCountForTesting(): number {
-  return 0;
-}
-
 /** Format the deferred tools prompt section. Shared by CLI and engine prompt assemblers. */
 export function formatDeferredToolsSection(
   tools: ReadonlyArray<{ name: string; description: string }>,