Function validateCommand

validateCommand(
    patterns: readonly string[],
    cliOptions: ValidateCliOptions,
    prompter?: FixPrompter,
): Promise<void>
CLI command handler for validate operations.

Processes markdown files to find broken links of all types. Supports various output formats and filtering options.
Parameters
- patterns: readonly string[]
  File patterns to validate
- cliOptions: ValidateCliOptions
  CLI-specific options
- Optionalprompter: FixPrompter
  Chooses a suggestion for each broken link in fix mode; defaults to a terminal prompt
Returns Promise<void>
Example
```
# Validate all markdown files including external links
markmv validate "**/*.md" --check-external --verbose

# Check only internal links and images
markmv validate docs/ --link-types internal,image --strict-internal

# Find broken links with context information
markmv validate README.md --include-context --group-by type
```
- Defined in commands/validate.ts:733