feat: add text processing with media payloads

[gabewillen]

Summary

• add CortextWasm.processTextWithMedia using the media-capable JSON C API
• preserve arbitrary binary bytes and MIME metadata via the wasm cortext_media ABI struct
• add TypeScript Media type, unit coverage, README and changelog documentation

Compatibility

• existing processText path is unchanged
• requires a WASM asset built from the media-capable core C API, including _cortext_process_text_with_media_json_with_options
• null media passes a null descriptor and keeps no-payload behavior

Validation

• npm run typecheck
• npm run test:unit (18 passed)
• npm test (19 passed; smoke context skipped because vendored 1.2.0 asset lacks model)
• npm run pack:check
• npm run check:wasm

Core C API/export update is tracked in the companion core PR.

[Copilot]

Pull request overview

Adds a new WASM binding entrypoint for processing canonical text while attaching an arbitrary binary “media” payload (bytes + MIME type), using the media-capable JSON C API to avoid string/base64 coercion.

Changes:

• Add CortextWasm.processTextWithMedia(...) that marshals cortext_media + options structs into WASM memory and calls _cortext_process_text_with_media_json_with_options.
• Introduce and export a new TypeScript Media type and update the Emscripten module typings for the new export.
• Add unit coverage plus README/CHANGELOG documentation for the new API.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/unit.test.mjs	Extends the fake Emscripten module and adds unit tests asserting correct ABI marshalling and retention validation.
src/types.ts	Adds Media type and declares the new C export on CortextEmscriptenModule.
src/index.ts	Re-exports the new Media type from the package entrypoint.
src/cortext-wasm.ts	Implements processTextWithMedia and adds a helper to write uint32 fields into WASM memory.
README.md	Documents the new API and provides a usage example.
CHANGELOG.md	Notes the new API addition.

Suppressed comments (1)

src/cortext-wasm.ts:272

• After introducing the processWithMedia runtime check, call the validated local function reference so this continues to typecheck if _cortext_process_text_with_media_json_with_options is made optional on the module interface.

        this.#readRawJson(
          this.module._cortext_process_text_with_media_json_with_options(
            handle,
            textPtr,
            sourcePtr,
            mediaPtr,
            optionsPtr
          )

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