Module dotenv/edit/types

Dotenv editor types (format-preserving).

Requirements addressed:

• Provide a format-preserving dotenv edit surface (pure text pipeline + FS adapter).
• Preserve comments/blank lines/unknown lines and separator spacing; support merge vs sync.
• Deterministic target selection across getdotenv paths with optional template bootstrap.

Notes:

• The parser intentionally preserves unknown lines verbatim rather than rejecting them.
• The editor focuses on .env-style KEY=VALUE lines; anything not recognized is preserved as raw text.