Catalog Md Format

catalog-format — Added reading the catalog as Markdown

The catalog-format experiment gains a second non-interactive format. Where --format=jsonl writes a record per catalog entry for a program to parse, --format=md writes one Markdown document for a person or an agent to read:

terragrunt catalog --experiment=catalog-format --format=md > catalog.md

Each entry becomes a section holding the metadata the catalog user interface shows for it, the source the component is scaffolded from, and the component's README. Sections are written as entries are discovered, so the document is readable while the remaining repositories are still loading.

READMEs are reproduced inside fenced blocks, so the headings one carries are not read as sections of the catalog document. The document closes with a table naming every component it holds and a count of what was discovered, which is how a reader tells a complete document from one that was cut short by a consumer that stopped reading.

For the fields each section carries, see Non-interactive catalog.