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/input-controller-large-paste.test.ts

@@ -1,3 +1,4 @@
+import { removeWithRetries } from "@oh-my-pi/pi-utils";
 /**
  * Large-paste menu: when a paste reaches the configured `paste.largeMenuThreshold` line count,
  * the editor's `onLargePaste` hook routes through `InputController.handleLargePaste`, which offers
@@ -116,7 +117,7 @@ describe("InputController.presentLargePasteMenu file attachment", () => {
 	let dir: string | undefined;
 
 	afterEach(async () => {
-		if (dir) await fs.rm(dir, { recursive: true, force: true });
+		if (dir) await removeWithRetries(dir);
 		dir = undefined;
 	});