Handle empty search queries

[rbjornstad]

Summary

• return user-scoped default results for empty search queries instead of relying on an empty Bleve conjunction
• rank empty-search defaults by kind so teams come first, then applications, jobs, and other resources
• add focused search tests for empty-query defaults, filtering, no-team users, and ranking

Testing

• rtk go test ./internal/search
• rtk mise run test:unit
• rtk mise run fmt

[Copilot]

Pull request overview

This PR updates the Bleve-backed search implementation to treat an empty search query as “default results”, returning only user-team–scoped documents and ranking those defaults by resource kind (teams first). It also adds a focused test suite for the empty-query behavior.

Changes:

• Add explicit handling for empty queries: return no defaults for users without teams; otherwise constrain results to the user’s team slugs.
• Extend boosting for empty queries to include kind-based ranking (TEAM > APPLICATION > JOB > others).
• Add unit tests covering empty-query defaults, ranking, team filtering within user teams, and no-team users.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/search/bleve.go	Implements empty-query default behavior (user-team scoping) and adds kind-based boosting for deterministic default ranking.
internal/search/bleve_test.go	Adds unit tests validating empty-query defaults, filtering behavior, no-team behavior, and ranking order.