feat: smart save_to with full path support and bug fix

[mikesoennichsen]

Summary

Three changes to the save_to parameter:

1. Bug fix: When markdown is a raw string (e.g. chaining parse() → extract()), the
   output filename is now output_extract_output.json instead of garbage derived from the
   markdown content. All string inputs are treated as content, not file paths — file inputs
   should use Path objects, tuples, or IO objects.

2. Full path support: save_to now accepts a full file path ending in .json in addition
   to a directory. Directory mode auto-generates the filename as before.

   # Directory mode (existing behavior)
   client.extract(markdown=Path("doc.pdf"), save_to="./output")
   # → ./output/doc_extract_output.json
   
   # Full path mode (new)
   client.extract(markdown=result.markdown, save_to="./output/my_result.json")
   # → ./output/my_result.json

3. Async support: Added save_to to AsyncLandingAIADE.extract(), .parse(), and .split().

Test plan

• 28 unit tests passing (filename extraction, full-path mode, async methods)
• ruff check clean
• Manual: chain parse() → extract() with both save_to modes

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR enhances response saving ergonomics by allowing save_to to accept either an output directory (existing behavior) or an explicit .json file path (new behavior), and extends save_to support to async client methods. It also adjusts filename inference to avoid treating raw markdown strings as file paths.

Changes:

• Update _save_response to support save_to as either a directory or a full .json output path.
• Refine _get_input_filename behavior for str inputs to reduce accidental filename derivation from raw markdown.
• Add save_to support to async extract, parse, and split, plus expanded test coverage.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/landingai_ade/_client.py	Implements full-path .json save support, updates filename inference, and adds async save_to handling.
tests/test_save_to.py	Adds tests for raw-markdown filename inference, full-path save behavior, and async save_to support.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

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