[Bug]: [Presets] Resume requires literal env values in the local environment

[peterschmidt85]

Steps to reproduce

1. Start a preset creation from a configuration with a literal env value:

   env:
   - MODEL_LABEL=some-value

2. Interrupt it.
3. Resume from a shell where MODEL_LABEL is not set: dstack preset resume <id>.

Actual behaviour

Environment variable MODEL_LABEL is not set

The session record stores env by name only, so on resume the literal reads back as a passthrough that must resolve from the local environment.

Expected behaviour

dstack preset resume <id> resumes with MODEL_LABEL=some-value from the recorded configuration.