feat: add worktree isolation utilities for parallel sessions

[reshashi]

Summary

Adds two utility scripts for managing isolated git worktrees, enabling multiple Claude Code sessions to work on different tasks without file conflicts:

• scripts/worktree.sh — create/list/remove/clean worktrees with .claude-worktree marker files for branch tracking
• scripts/branch-guard.sh — prevents accidental commits to the wrong branch by validating the .claude-worktree marker against the current git branch

These complement conductor.json for multi-session orchestration by providing the underlying worktree isolation layer. Conductor is the conductor; these are the tracks.

Usage

# Create isolated worktree for a task
scripts/worktree.sh create myapp auth-flow main

# List active worktrees with branch info
scripts/worktree.sh list myapp

# Remove worktree and delete branch
scripts/worktree.sh remove myapp auth-flow

# Clean all worktrees for a project
scripts/worktree.sh clean myapp

Branch guard (for git hooks)

# In pre-commit hook:
scripts/branch-guard.sh --check-only
# Exit 0 = OK, Exit 1 = wrong branch (blocks commit)

The .claude-worktree marker file (JSON) tracks expected branch, worktree path, session name, and creation timestamp. It is auto-added to .gitignore on creation.

Environment

GSTACK_WORKTREE_BASE overrides the default worktree root (~/.worktrees).

Test plan

• worktree.sh create creates worktree + branch + .claude-worktree marker
• worktree.sh list shows branch and creation time from marker
• worktree.sh remove cleans up worktree, branch, and directory
• branch-guard.sh returns 0 when on correct branch
• branch-guard.sh returns 1 when on wrong branch or main/master
• branch-guard.sh returns 0 when no marker found (not in a worktree)

🤖 Generated with Claude Code