Resolve model package paths and path-valued session options through ONNX Runtime

[jambayk]

Summary

Builds on model package loading (#2227) so onnxruntime-genai resolves every path reference in a variant's genai_config.json through ONNX Runtime's model package resolver. A variant can reference its weights, an EP context file, and shared assets (such as tokenizer or processor config) by sha256: shared-asset URI or relative path, and ONNX Runtime owns shared-asset resolution and path confinement.

What changed

• Delegate genai_config.json path resolution to ORT's ModelPackage_ResolveStringRef when the model is loaded from a package, so sha256: shared-asset references and relative paths resolve consistently with the package rules. Config::ResolvePath now rejects a sha256: reference when the model is a plain directory, with a clear error, instead of producing a bogus path.
• Resolve path-valued session options against the package. The external initializers folder (session.model_external_initializers_file_folder_path) and the EP context file path (ep.context_file_path) declared in a variant's session_options are resolved before being applied, so a variant can point at weights or a context file stored in a shared asset. For models loaded from memory, the external initializers folder defaults to the config directory only when the config did not already set it.
• Resolve the OrtModelPackageApi experimental functions self-contained in GetModelPackageApi(), so genai does not vendor ONNX Runtime's experimental C++ header.
• Author packages with schema_version "1.0".

[Copilot]

Pull request overview

This PR extends the model-package loader so that all path references originating from a package variant’s genai_config.json (including sha256: shared-asset URIs and relative paths) are resolved via ONNX Runtime’s model package resolver, and additionally resolves path-valued session options before applying them to ORT.

Changes:

• Delegate genai_config.json path resolution to ORT’s ModelPackage_ResolveStringRef when loading from a package, and reject sha256: references when loading from a flat directory.
• Resolve path-valued session option entries (notably session.model_external_initializers_file_folder_path and ep.context_file_path) via Config::ResolvePath before applying them.
• Update tests + docs for the inline-component package layout and sha256: shared assets.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/model_package_test.cpp	Updates package fixture authoring and adds E2E tests for sha256: tokenizer + external initializer folder resolution.
src/models/onnxruntime_inline.h	Adds HasConfigEntry wrapper and resolves model package experimental function pointers by name (incl. ResolveStringRef).
src/models/onnxruntime_api.h	Exposes HasConfigEntry and extends the model package API wrapper with ModelPackage_ResolveStringRef.
src/models/model.cpp	Resolves path-valued session options and adjusts external-initializers defaulting for in-memory loads; wires package resolver into Config.
src/models/model_package.h	Keeps the package context alive in the load result for deferred path resolution.
src/models/model_package.cpp	Stores the opened package context in the load result.
src/config.h	Adds package_resolver callback used when loading from a package.
src/config.cpp	Reworks ResolvePath to delegate to ORT when in a package; rejects sha256: in flat directories.
docs/model_package.md	Updates documentation to describe inline components and sha256: shared assets.

Comments suppressed due to low confidence (1)

src/models/onnxruntime_inline.h:1575

• Ort::GetModelPackageApi() only checks CreateModelPackageContext for availability. If an ONNX Runtime build has the model package API but lacks the newer ModelPackage_ResolveStringRef entry, later calls through ResolveStringRef() will dereference a null function pointer and crash. Guard for ModelPackage_ResolveStringRef (and ideally any other required entries) and fail with a clear error early.

  if (fns.CreateModelPackageContext == nullptr) {
    throw std::runtime_error(
        "Model package API is not available in this ONNX Runtime build. "
        "Model packages require ONNX Runtime with the OrtModelPackageApi experimental functions.");
  }