feat(projects): support marked_for_deletion_on filter on browse_projects (Premium+)

[polaz]

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Problem

GitLab 17.1 added the marked_for_deletion_on=YYYY-MM-DD filter on GET /projects, allowing admins to list projects scheduled for purge on a specific date. Useful for last-minute restore campaigns. Currently we can't filter listed projects by deletion date.

Investigation done (current state)

Verified against src/entities/:

• ✅ entities/shared.ts:83-84 already parses marked_for_deletion_at and marked_for_deletion_on fields on project response
• ❌ No grep hit using either field as filter parameter in any request
• Related: pairs with feat(projects): browse_projects action 'list_deleted' for soft-deleted projects #431 (list_deleted)

Re-verify before coding:

grep -rn 'marked_for_deletion' src/

Acceptance criteria

• New optional markedForDeletionOn?: string (ISO date YYYY-MM-DD) param on browse_projects list action
• Tier-gated: requires Premium/Ultimate — use existing tier detection, return clear error otherwise
• Combines naturally with include_pending_delete=true from feat(projects): browse_projects action 'list_deleted' for soft-deleted projects #431
• Integration test gated on Premium tier via existing tier-gate helper

GitLab API

• Endpoint: GET /api/v4/projects?marked_for_deletion_on=YYYY-MM-DD (combined with include_pending_delete=true)
• Tier: Premium/Ultimate
• Version: 17.1+
• Docs: https://docs.gitlab.com/api/projects/
• Related upstream: https://gitlab.com/gitlab-org/gitlab/-/issues/463939

Estimate

1h

Context

Found during GitLab 18→19 API landscape analysis.