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/update-cli.test.ts

@@ -12,6 +12,7 @@ import {
 	resolveUpdateMethodForTest,
 	sweepStaleBackups,
 } from "@oh-my-pi/pi-coding-agent/cli/update-cli";
+import { removeWithRetries } from "@oh-my-pi/pi-utils";
 
 const tempDirs: string[] = [];
 
@@ -22,7 +23,7 @@ async function makeTempDir(): Promise<string> {
 }
 
 afterEach(async () => {
-	await Promise.all(tempDirs.splice(0).map(dir => fs.rm(dir, { recursive: true, force: true })));
+	await Promise.all(tempDirs.splice(0).map(dir => removeWithRetries(dir)));
 });
 describe("update-cli install target detection", () => {
 	it("uses bun update when prioritized omp is inside bun global bin", () => {