Add git workflow instructions to prevent rebase issues with Copilot agents

[Copilot]

Copilot agents don't handle git rebase well, causing commit and diff corruption. This adds explicit instructions to use merge strategies instead.

Changes

• AGENTS.md: Added "Git Workflow" section under Technical Guidelines with rebase prohibition
• .github/copilot-instructions.md: Added matching git workflow instructions for consistency

Instructions Added

**IMPORTANT: When working with git branches and updates:**
- **DO NOT use `git rebase`** - Copilot agents don't work well with rebase operations
- **USE `git merge` or `git merge --ff` instead** - Use merge or fast-forward merge to integrate changes
- When updating your branch with changes from the main branch, use:
  - `git merge origin/main` (creates a merge commit)
  - `git merge --ff origin/main` (fast-forward if possible)

Fixes KUL-459

Original prompt

Issue Title: Update AGENTS.md and copilot instruction
Issue Description: Since Copilot is not working well with rebase, tell them when we're talking about rebase please do merge or merge fast forward so it's no messing up with the commits and diff.
Fixes https://linear.app/kulkul/issue/KUL-459/update-agentsmd-and-copilot-instruction

Comment by User 592887fc-2770-458d-9cb2-6c408eb732f1:
https://github.com/kulkultech/jumpstart-swe

Comment by User 4d883eba-0c72-4e22-84fc-717aaa2ef283:
📋 I wasn't able to determine which GitHub repository to work in.

I think it's one of these, but can you tell me which one is right?

Comment by User :
This thread is for an agent session with githubcopilot.

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.