Feature: Markdown table output format (--markdown)

[dlevy-msft-sql]

Summary

Add a --markdown flag to output query results as Markdown tables.

Use Case

• Copy/paste results directly into GitHub issues, PRs, or documentation
• Generate documentation from database queries
• Integration with documentation pipelines

Proposed Syntax

sqlcmd -S server -Q "SELECT * FROM users" --markdown

Example Output

| id | name | email |
|----|------|-------|
| 1 | Alice | alice@example.com |
| 2 | Bob | bob@example.com |

Implementation Notes

• Could leverage existing formatter infrastructure in pkg/sqlcmd/formatter.go
• Similar approach to how XML output is handled