chore(skills): start-sprint uses current branch as team

No argument needed — the current branch determines the team.
Only asks if on main.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/start-sprint/SKILL.md

@@ -16,19 +16,20 @@ briefing, and present actionable next steps.
 
 ## Workflow
 
-### 1. Determine the team branch
+### 1. Determine the team
 
-If the user provided a branch name as argument, use it. Otherwise use the
-current branch (`git branch --show-current`). Valid team branches: `server`,
-`client`.
+The current branch IS the team. Read it with:
+```bash
+git branch --show-current
+```
 
-If on `main`, ask the user which team branch to start.
+Valid team branches: `server`, `client`. If on `main`, ask the user which
+team branch to check out first.
 
-### 2. Sync the branch
+### 2. Sync with main
 
 ```bash
 git fetch --all
-git checkout <branch>
 git merge origin/main --no-edit
 ```