fix: awk injection vulnerability in get_worktree_path

[RodrigoEspinosa]

🎯 What: The vulnerability fixed
Using awk -v b="$branch" in get_worktree_path allowed awk to evaluate escape sequences in the $branch variable, leading to AWK injection if the branch name contained backslashes.

⚠️ Risk: The potential impact if left unfixed
An attacker or malicious repository could use specially crafted branch names with backslashes to trigger unexpected behavior or execute unintended logic when awk processes the input, potentially exposing the user to command injection or unauthorized data access.

🛡️ Solution: How the fix addresses the vulnerability
Replaced the vulnerable -v variable assignment with an environment variable approach. Specifically, used BRANCH="$branch" awk -F'\t' '$1 == ENVIRON["BRANCH"] { print $2 }'. This ensures awk treats the input as a literal string without evaluating embedded escape sequences. Added a BATS test to confirm proper handling of backslashes in branch names.

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PR created automatically by Jules for task 1842531871741686573 started by @RodrigoEspinosa

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