fix: remove empty fields from dashboard chat context

[AdityaHegde]

Analyst agent args had a lot of empty values. This gets especially bad when filters are present and every level has things like name: "", cond: null etc. Adding omitempty to make json marshaller remove empty fields.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!