Refine release drafter output with contributor sections and single-category PR placement

[Copilot]

This updates release drafting to explicitly recognize first-time contributors and list all release contributors, while reducing duplicated PR entries across sections. PRs are now more likely to appear in one primary category instead of being repeated due to broad auto-label matches.

• Release notes structure

  • Added a dedicated 🌱 New Contributors category keyed to first-time-contributor.
  • Extended the release template with a ## Contributors section using $CONTRIBUTORS.

• Category de-duplication behavior

  • Removed broad autolabel rules that commonly caused overlap across categories:
    • dropped file-based docs autolabeling (*.md)
    • dropped title-keyword autolabeling for feature/bugfix
  • Kept branch-based autolabeling so categorization remains intentional and predictable.

• Config update (excerpt)

  categories:
    - title: "🌱 New Contributors"
      labels:
        - "first-time-contributor"
  
  template: |
    ## What's Changed
  
    $CHANGES
  
    ## Contributors
  
    $CONTRIBUTORS

[Copilot]

Pull request overview

Updates the repository’s Release Drafter configuration to improve release note structure by adding contributor-focused sections and reducing label overlap that can cause PRs to appear in multiple categories.

Changes:

• Added a 🌱 New Contributors release-notes category keyed to the first-time-contributor label.
• Simplified autolabeler rules by removing broad file/title-based label triggers to reduce multi-category labeling.
• Extended the release template to include a ## Contributors section via $CONTRIBUTORS.

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