feat: add output file option for dry-run mode and improve error handling

[nahuel11500]

No description provided.

[Copilot]

Pull Request Overview

This PR adds support for output file option in dry-run mode and improves error handling. The main purpose is to enhance the dry-run functionality by allowing users to save the generated JSON to a file instead of only printing to stdout, while also making the tool more robust in dry-run scenarios by relaxing validation requirements.

Key changes:

• Added OutputFile configuration option for writing dry-run output to a file
• Improved dry-run mode by skipping Notion API client initialization and validation when not needed
• Enhanced table support with proper Notion API table block structures
• Better error handling and progress reporting for block operations

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/run/run.go	Added OutputFile config field, improved dry-run validation logic, and enhanced block deletion progress reporting
internal/notion/types.go	Extended Block type with table support and improved JSON serialization
internal/notion/client.go	Reduced chunk size for better reliability with large documents
internal/markdown/convert.go	Added comprehensive table conversion support and improved image URL validation
cmd/notion-md/main.go	Added output-file flag and updated help text for dry-run usage
README.md	Updated command examples and documentation to reflect new features

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}