fix: ensure roles and connections are always resolved from defaults in getConnEnvOptions

[pyramation]

Summary

Fixes TypeError: Cannot read properties of undefined (reading 'anonymous') when running pgpm admin-users bootstrap.

The root cause was that getConnEnvOptions() could return undefined for roles and connections if a config file or environment explicitly set these to undefined, bypassing the deepmerge defaults. This PR:

1. Fixes the merge logic in getConnEnvOptions to explicitly spread defaults for roles and connections, ensuring they're always resolved
2. Adds defensive validation in SQL generators to throw clear errors if roles/connections are undefined
3. Adds tests to prevent regression

Review & Testing Checklist for Human

• Verify the getConnEnvOptions change doesn't break existing config overrides - the tests show partial overrides still work, but worth confirming with your actual config files
• Test pgpm admin-users bootstrap --yes works with the fix
• Test pgpm admin-users add and pgpm admin-users remove still work (they use the same SQL generators)
• Consider if there are other places in the codebase that might have similar issues with optional nested properties not being resolved from defaults

Recommended test plan:

# Run the command that was failing
pgpm admin-users bootstrap --yes

# Verify other admin-users commands work
pgpm admin-users add --username testuser --password testpass --yes
pgpm admin-users remove --username testuser --yes

Notes

• The exact root cause of why deepmerge wasn't preserving defaults wasn't fully determined (could be a config file setting db.roles: undefined, version mismatch in global install, etc.). This fix ensures defaults are always applied regardless.
• Added jest.config.js to pgpm/env package to enable running the new tests

Link to Devin run: https://app.devin.ai/sessions/3a8e8acb237e4b08bc1878defcf041f0
Requested by: Dan Lynch (@pyramation)

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