Simplify worktree branch naming: use worktree name directly instead of worktree- prefix

Current Behavior

When using the --worktree <name> CLI flag, Claude Code creates a git branch
named worktree-<name>. For example:

claude --worktree test

Creates a branch called worktree-test.

Desired Behavior

The branch should be named exactly as specified, without the worktree- prefix:

claude --worktree test

Should create a branch called test.

Motivation

• The worktree name is already semantically meaningful — the prefix is redundant
• Conflicts with team branch naming conventions (e.g., feat/x, task-1)
• Reduces cognitive overhead: worktree name and branch name can be identical
• Cleaner git history and PR names