fix(core): resolve relative local-channel conda paths in lock files

[hunger]

Fixes: #6322.

Needs conda/rattler#2498

How Has This Been Tested?

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  • I have tested any AI-generated content in my PR.
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Tools: Claude

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added sufficient tests to cover my changes.
• I have verified that changes that would impact the JSON schema have been made in schema/model.py.