- Add GC_MODE=false variable and --gc) case to flag parsing
- Define gc_instances() before --check block (callable before ANSI init)
- Add GC dispatch block after --check, before ANSI formatting (early exit)
- gc_instances iterates ~/.claudebox/projects/*/project-root, removes dirs
whose recorded root path no longer exists on disk
- Prints each removal and summary count to stderr (D-11, D-12, INST-04)
- Add CREDS_FILE/CREDS_MOUNT detection after mkdir ~/.claudebox
- Conditional --bind in exec bwrap via BWRAP_ARGS array
- Mirror conditional bind in --dry-run display block
- Read-write mount (not ro-bind) for OAuth token refresh
- Silent skip when credentials file absent (no error/warning)
- Refactor exec bwrap to BWRAP_ARGS array for conditional mount support
