v0.5.0

Added

• Per-step env field on bootstrap steps, hooks, and services with $(…) shell interpolation
• Env values containing $(…) are evaluated at runtime (not config load time) via sh -c
• Step-level env merges on top of global env — step values win on conflict
• Shell interpolation runs in the step's working directory for correct relative path resolution
• Failed $(…) commands produce an empty string and log a warning; the step continues normally

Changed

• Introduced config.Env named type with Merge and ToSlice methods, replacing raw map[string]string
• Service env values now support $(…) interpolation (previously only literal values)