[task] Add directory ingestion helper for supported text files

[AlexanderGardiner]

Checks

• I searched open and closed issues and pull requests and did not find a duplicate.

Area

Source

Goal

Add a small helper for ingesting a directory of supported files so users can load a folder of .txt and Markdown documents without manually iterating through paths.

Once Anchor.ingest_file(path) exists, directory ingestion is the next ergonomic layer. It should stay narrow and predictable: discover supported files, call the existing file ingestion path, and return the IDs that were created.

Suggested file locations

• src/anchor/anchor.py
• src/anchor/extractors/detect.py only if helper behavior needs shared support
• tests/unit/test_anchor_directory_ingest.py
• tests/fixtures/ingestion/

Scope

Add a public directory ingestion helper for supported text-based files.

The implementation should:

• Add a method such as Anchor.ingest_directory(path).
• Accept a str | Path directory path.
• Recursively discover supported .txt, .md, and .markdown files.
• Skip unsupported file extensions by default.
• Call Anchor.ingest_file(...) for each supported file.
• Return the created chunk IDs in a deterministic order.
• Preserve existing Anchor.ingest_text(...) and Anchor.ingest_file(...) behavior.

Out of scope

• Do not add PDF, Word, or source-code ingestion.
• Do not add URL ingestion.
• Do not add file watching.
• Do not add ignore-file parsing.
• Do not add concurrency.
• Do not introduce new dependencies.
• Do not change MemoryStore.

Definition of done

• Anchor.ingest_directory("docs/") ingests supported .txt and Markdown files.
• Unsupported files in the directory are skipped without blocking supported files.
• Returned chunk IDs are deterministic relative to sorted file traversal.
• Nested directories are handled recursively.
• Tests cover mixed supported/unsupported files.
• Tests cover nested directories.
• Existing file and text ingestion behavior continues to pass.

[github-actions]

Potentially related existing work:

• [task] Add public Anchor.ingest_file(path) API #76 [task] Add public Anchor.ingest_file(path) API (open)

If one of these is the canonical thread, comment there and a maintainer can close this issue with /duplicate #123.