Add verified queries (draft)

[rlittle08]

Extends the spec for new section - verified_queries.

What will this be used for?

• For humans: documenting approved query patterns within a semantic model
• For AI: In tools like Cortex Analyst in Snowflake, will be directly used for query generation by AI tools

Why does it warrant inclusion in this spec?

• For both use cases listed above, example queries are universally helpful
• Having a namespace defined in the standard supports interoperable use, and allows data vendors to share proper query patterns with multiple downstream applications (AI or otherwise), in one place

[GabrielBarberini]

+1 from a downstream consumer migrating a proprietary cookbook (~25 named SQL templates). Two gaps:

1. Typed parameters. Without them, verified_queries is fixed SQL, not a reusable template. Suggested:

- name: top_n_by_category
  question: "Top N items for {category}?"
  parameters:
    - name: category
      datatype: string          # leans on https://github.com/open-semantic-interchange/OSI/pull/113
      description: "category code"
      sample_values: ["A", "B", "C"]
    - name: days
      datatype: integer
      default: 30
    - name: n_limit
      datatype: integer
      default: 10
  expression:
    dialects:
      - dialect: ANSI_SQL
        expression: |
          SELECT ... LIMIT {n_limit}

2. Placeholder convention. Pin one ({name} / :name / ${name}) so consumers can substitute deterministically.