Fix Claude auth detection with custom config directories

[sox8502]

Summary

• import Claude Code's native CLAUDE_CONFIG_DIR from the interactive shell when the macOS app starts
• use that same profile for auth metadata, skill installation, and every spawned Claude process
• preserve Claude's default ~/.claude plus ~/.claude.json layout when no override is set

Fixes OR-207.

Test checklist

• cargo fmt --all --check
• cargo clippy --all-targets -- -D warnings
• cargo build --locked
• cargo test --locked (620 passed, 1 live-cluster test ignored)
• Four independent read-only Claude reviewers returned NO BLOCKERS
• Verify a Finder-launched macOS app uses a custom shell-exported CLAUDE_CONFIG_DIR