Create git-workflow skill

Summary

Create a skill for git operations in the omnirepo, covering git-branchless workflow and commit hygiene.

Source Material

From Omni/Ide/README.md:

• Uses git-branchless for patch-based workflow
• Key commands: smartlog, amend, move, restack
• Commit hygiene: small focused commits, descriptive messages
• Required checks before completing tasks

Skill Content

---
name: git-workflow
description: Git operations for the omnirepo using git-branchless. Use when committing, branching, or managing changes.
---

# Git Workflow

This repo uses **git-branchless** for a patch-based workflow.

## Key Commands

### View commit graph
\`\`\`bash
git smartlog
\`\`\`

### Create a commit
\`\`\`bash
git add .
git commit -m "Namespace: Short description"
\`\`\`

### Amend current commit
\`\`\`bash
git add .
git amend
\`\`\`

### Move/restack commits
\`\`\`bash
git move -s <source> -d <destination>
git restack
\`\`\`

## Commit Message Format

\`\`\`
Namespace: Short description (max 72 chars)

Longer explanation if needed. Explain why, not just what.

Task-Id: t-123
\`\`\`

Example:
\`\`\`
Omni/Task: Add --namespace flag to create command

Allows associating tasks with specific code namespaces for
better organization and filtering.

Task-Id: t-456
\`\`\`

## Before Committing

Always run:
\`\`\`bash
bild --test <namespace>
lint <namespace>
\`\`\`

Fix all errors before committing.

## What NOT to Do

- ❌ `git push` without explicit user request
- ❌ `git pull` without explicit user request
- ❌ Force pushes or destructive operations
- ❌ Large commits mixing unrelated changes

Deliverables

• [ ] Omni/Ide/Git.md
• [ ] Test with actual git operations