Filter undefined values from env format output

[Copilot]

dmno resolve --format env was serializing undefined values as KEY="undefined" while --format json correctly excluded them. This inconsistency caused invalid env file output.

Changes:

• Filter undefined values in stringifyObjectAsEnvFile before serialization
• Add test coverage for undefined value handling

Before:

$ dmno resolve --format env
BILLING_TEAMS_HOOK_URL="undefined"

After:

$ dmno resolve --format env
# BILLING_TEAMS_HOOK_URL excluded from output

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.iconify.design

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
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Original prompt

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This section details on the original issue you should resolve

<issue_title>[BUG]: undefined items in env format output</issue_title>
<issue_description>### dmno version

0.0.39

Steps to reproduce

What is expected?

keys with undefined values should not be present in dmno resolve --format env

What is actually happening?

actual output is KEY="undefined"

System Info

Any additional comments?

No response</issue_description>

<agent_instructions>make the dmno resolve --format env output also exclude any undefined items as it does for the json output</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [BUG]: undefined items in env format output #234

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[changeset-bot]

🦋 Changeset detected

Latest commit: e7974ca

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
dmno	Patch

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commit: e7974ca