feat: add text processing with media

[gabewillen]

Adds Python bindings for Cortext text processing with optional binary media and MIME types.

Tests: .venv/bin/pytest -q (9 passed).

[Copilot]

Pull request overview

Adds a new Python API surface for processing text with optional binary media attachments (plus MIME type), wiring up the corresponding native entrypoints and documenting the new usage.

Changes:

• Add Cortext.process_text_with_media_json() / Cortext.process_text_with_media() methods that marshal optional media into _NativeMedia and call the native “with options” function.
• Extend native library configuration to detect and type the optional text+media symbols.
• Add a unit test to verify that binary bytes + MIME type are forwarded into the native media struct, and document the feature in the README.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
cortext/__init__.py	Adds native symbol detection/ctypes signatures and the new process_text_with_media* methods.
tests/test_cortext.py	Adds a unit test that validates media bytes + MIME type marshalling into _NativeMedia.
README.md	Documents how to call process_text_with_media with Media(...) or raw bytes + media_mimetype.

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