docs: add fork configuration guidance to CONTRIBUTING.md (#1364)

Add "Working with Forks" section addressing common issues when:
- Setting up a fork initially
- Keeping forks synced with upstream
- Converting a fork to standalone repository

Includes troubleshooting table for common git remote issues.
This addresses an RCA finding where contributors hit issues after
making their fork standalone without updating local git config.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

CONTRIBUTING.md

@@ -16,6 +16,7 @@ Thank you for your interest in contributing to Auto Claude! This document provid
 - [Testing](#testing)
 - [Continuous Integration](#continuous-integration)
 - [Git Workflow](#git-workflow)
+  - [Working with Forks](#working-with-forks)
   - [Branch Overview](#branch-overview)
   - [Main Branches](#main-branches)
   - [Supporting Branches](#supporting-branches)
@@ -517,6 +518,72 @@ npm run typecheck
 
 We use a **Git Flow** branching strategy to manage releases and parallel development.
 
+### Working with Forks
+
+When contributing to Auto Claude, you'll typically fork the repository first. Proper fork configuration is essential to avoid sync issues.
+
+#### Initial Fork Setup
+
+```bash
+# 1. Fork on GitHub (click the Fork button on the repo page)
+
+# 2. Clone YOUR fork (not the original repo)
+git clone https://github.com/YOUR-USERNAME/Auto-Claude.git
+cd Auto-Claude
+
+# 3. Verify your remotes point to YOUR fork
+git remote -v
+# Should show:
+# origin  https://github.com/YOUR-USERNAME/Auto-Claude.git (fetch)
+# origin  https://github.com/YOUR-USERNAME/Auto-Claude.git (push)
+
+# 4. Add upstream remote to sync with the original repo
+git remote add upstream https://github.com/AndyMik90/Auto-Claude.git
+```
+
+#### Keeping Your Fork Updated
+
+```bash
+# Fetch latest changes from upstream
+git fetch upstream
+
+# Sync your develop branch with upstream
+git checkout develop
+git merge upstream/develop
+git push origin develop
+```
+
+#### Converting a Fork to Standalone
+
+> ⚠️ **Common Issue:** After making a fork standalone (e.g., disconnecting from the original repo on GitHub), your local git configuration may still reference the original forked repository, causing push/pull issues.
+
+If you convert your fork to a standalone repository:
+
+```bash
+# 1. Update origin to point to your standalone repo
+git remote set-url origin https://github.com/YOUR-USERNAME/Your-Standalone-Repo.git
+
+# 2. Remove the upstream remote (no longer applicable)
+git remote remove upstream
+
+# 3. Verify your configuration
+git remote -v
+# Should only show your standalone repo as origin
+
+# 4. Update your default branch tracking if needed
+git branch --set-upstream-to=origin/main main
+git branch --set-upstream-to=origin/develop develop
+```
+
+#### Troubleshooting Fork Issues
+
+| Problem | Cause | Solution |
+|---------|-------|----------|
+| `Permission denied` on push | Origin points to upstream repo | `git remote set-url origin <your-fork-url>` |
+| `Repository not found` | Fork was deleted or made standalone | Update remote URL to current repo location |
+| Can't push to develop | Local branch tracks wrong remote | `git branch --set-upstream-to=origin/develop` |
+| Commits show wrong author | Git config not set | `git config user.email "you@example.com"` |
+
 ### Branch Overview
 
 ```