test(rules-core): isolate sisyphus deprecation warning assertion

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

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

packages/rules-core/src/finder.ts

@@ -10,6 +10,7 @@ import { log } from "../../../src/shared/logger";
 const SISYPHUS_DEPRECATION_MESSAGE = "[rules] .sisyphus/rules is deprecated and will be removed in v4.3.0; migrate to .omo/rules";
 const SISYPHUS_LEGACY_RULE_SOURCES: ReadonlySet<RuleSource> = new Set([".sisyphus/rules", "~/.sisyphus/rules"]);
 const warnedSisyphusRuleDirectories = new Set<string>();
+let logSisyphusRuleDeprecation: typeof log = log;
 
 export function findRuleFiles(
   projectRoot: string | null,
@@ -148,12 +149,21 @@ function warnSisyphusRuleDeprecation(source: RuleSource, path: string): void {
   const warningKey = dirname(path);
   if (warnedSisyphusRuleDirectories.has(warningKey)) return;
   warnedSisyphusRuleDirectories.add(warningKey);
-  log(SISYPHUS_DEPRECATION_MESSAGE, {
+  logSisyphusRuleDeprecation(SISYPHUS_DEPRECATION_MESSAGE, {
     event: "rules-sisyphus-deprecated",
     path,
   });
 }
 
+export function _setSisyphusRuleDeprecationLoggerForTesting(logger: typeof log): void {
+  logSisyphusRuleDeprecation = logger;
+}
+
+export function _resetSisyphusRuleDeprecationWarningStateForTesting(): void {
+  warnedSisyphusRuleDirectories.clear();
+  logSisyphusRuleDeprecation = log;
+}
+
 function validFileRealPath(filePath: string): string | null {
   if (!existsSync(filePath)) return null;
   try {

packages/rules-core/src/index.test.ts

@@ -1,7 +1,7 @@
 import { mkdirSync, rmSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import { afterEach, describe, expect, it, mock, spyOn } from "bun:test";
+import { afterEach, describe, expect, it } from "bun:test";
 
 import {
   clearProjectRootCache,
@@ -13,7 +13,7 @@ import {
   parseRuleFrontmatter,
   shouldApplyRule,
 } from "./index";
-import * as logger from "../../../src/shared/logger";
+import { _resetSisyphusRuleDeprecationWarningStateForTesting, _setSisyphusRuleDeprecationLoggerForTesting } from "./finder";
 
 let testRoot: string | null = null;
 
@@ -26,7 +26,7 @@ function createTestRoot(name: string): string {
 }
 
 afterEach(() => {
-  mock.restore();
+  _resetSisyphusRuleDeprecationWarningStateForTesting();
   if (testRoot) {
     rmSync(testRoot, { recursive: true, force: true });
     testRoot = null;
@@ -97,17 +97,20 @@ describe("rules-core", () => {
     mkdirSync(join(root, ".sisyphus", "rules"), { recursive: true });
     mkdirSync(join(root, "src"), { recursive: true });
     writeFileSync(legacyRulePath, "legacy");
-    const logSpy = spyOn(logger, "log").mockImplementation(() => {});
+    const warnings: Array<{ readonly message: string; readonly data: unknown }> = [];
+    _setSisyphusRuleDeprecationLoggerForTesting((message, data) => {
+      warnings.push({ message, data });
+    });
 
     // when
     findRuleFiles(root, root, join(root, "src", "index.ts"));
     findRuleFiles(root, root, join(root, "src", "index.ts"));
-    const warnings = logSpy.mock.calls.filter(
-      ([message, data]) => message === SISYPHUS_DEPRECATION_MESSAGE && isSisyphusDeprecationData(data, legacyRulePath),
+    const deprecationWarnings = warnings.filter(
+      ({ message, data }) => message === SISYPHUS_DEPRECATION_MESSAGE && isSisyphusDeprecationData(data, legacyRulePath),
     );
 
     // then
-    expect(warnings).toHaveLength(1);
+    expect(deprecationWarnings).toHaveLength(1);
   });
 
   it("#given a workspace directory has no project marker (no .git, no package.json, etc.) AND contains .omo/rules/ #when findRuleFiles is called #then the .omo/rules/ files are still discovered", () => {