feat(concerto): add one-click Concerto model formatter in editor header

[hemantch01]

Closes #829

Adds a Concerto formatting action to the Playground so users can canonicalize CTO models with one click, similar to the existing JSON formatting experience.

Changes

• Added formatConcertoModel(cto: string) utility using @accordproject/concerto-cto parser/printer pipeline.
• Added ConcertoFormatButton in the Concerto Model header and wired action to:
  • format current editorModelCto
  • update both setEditorModelCto and setModelCto
  • show toast on invalid CTO without mutating editor state.
• Added direct dependency declaration for @accordproject/concerto-cto.
• Added tests:
  • utility tests for valid format, idempotence, and invalid CTO throw
  • component tests for success path and invalid CTO no-op + error toast.

Screenshots or Video

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit.
• Vital features and changes captured in unit and/or integration tests
• Commits messages follow AP format
• Extend the documentation, if necessary
• Merging to main from fork:branchname

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[github-actions]

This PR is stale because it has been open 15 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[hemantch01]

@sanketshevkar any feedback??