Git hash-object fails with Remix routes containing $ characters - transforms $id to ..

## Description
The Claude Code Action fails when processing Remix route files that contain `$` characters in their directory names. The action transforms `$id` and `$fooId` into `..` (double dots) when calling `git hash-object`, causing file not found errors.

## Details
**Expected path**: `app/routes/app._app.foos.$fooId.bars.$Id.edit/route.jsx`
**Actual path being accessed**: `app/routes/app._app.foos..bars..edit/route.jsx`

## Environment
- **OS**: Ubuntu (GitHub Actions runner)
- **Action Version**: `@beta`
- **Repository**: Using Remix with nested route structure

## Steps to Reproduce
1. Create a Remix app with nested routes containing `$` parameters
2. Set up Claude Code Action with the standard workflow
3. Trigger the action on a PR containing these route files
4. Action fails when trying to compute SHA for files with `$` in path

## Expected Behavior
The action should properly handle `$` characters in file paths without transforming them to `..`

## Actual Behavior
`$` characters are being replaced with `..` causing file not found errors

## Possible Fix
The issue appears to be in the `fetcher.ts` file where filenames are being processed. The `$` characters need to be properly escaped or handled when passed to `git hash-object`.