fix: migrate coding-agent tests from fs.rm to removeWithRetries

Migrate 203 test files (356 call sites) from fs.rm/fs.rmSync to
removeWithRetries/removeSyncWithRetries to reduce EBUSY test failures
on Windows. removeWithRetries is now exported from @oh-my-pi/pi-utils.

The migration uses a regex-based approach that:
- Replaces fs.rm(path, { recursive, force }) → removeWithRetries(path)
- Replaces fs.rmSync(path, { recursive, force }) → removeSyncWithRetries(path)
- Replaces fs.rm(path) → removeWithRetries(path) (no options)
- Skips fs.rm/fs.rmSync inside template literals (bun --eval scripts)
- Adds imports to existing @oh-my-pi/pi-utils import or creates new one
- Removes unused fs imports where fs.rm was the only fs usage (4 files)

packages/coding-agent/test/edit-patch-unchanged-error.test.ts

@@ -6,6 +6,7 @@ import { resetSettingsForTest, Settings } from "@oh-my-pi/pi-coding-agent/config
 import { DEFAULT_FUZZY_THRESHOLD, executePatchSingle } from "@oh-my-pi/pi-coding-agent/edit";
 import type { FileDiagnosticsResult } from "@oh-my-pi/pi-coding-agent/lsp";
 import type { ToolSession } from "@oh-my-pi/pi-coding-agent/tools";
+import { removeWithRetries } from "@oh-my-pi/pi-utils";
 
 function makeSession(cwd: string): ToolSession {
 	return {
@@ -47,7 +48,7 @@ beforeEach(async () => {
 
 afterEach(async () => {
 	resetSettingsForTest();
-	await fs.rm(tempDir, { recursive: true, force: true });
+	await removeWithRetries(tempDir);
 });
 
 describe("executePatchSingle — post-write verification error path", () => {