[shuo-zhou]

Description

Add GFK and api map

Status

Ready

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• In-line docstrings updated and documentation docs updated.

[codecov]

Codecov Report

❌ Patch coverage is 98.63014% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.68%. Comparing base (7bd85cd) to head (9637d7a).

Files with missing lines	Patch %	Lines
kalelinear/transformer/_gfk.py	98.57%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   90.40%   90.68%   +0.28%     
==========================================
  Files          25       26       +1     
  Lines        2000     2071      +71     
==========================================
+ Hits         1808     1878      +70     
- Misses        192      193       +1     

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[Copilot]

🟢 Approval recommended

The implementation, API integration, tests, and documentation are consistent, with no unresolved blocking findings.

No open issues 🎉

What changed in this PR

Adds Geodesic Flow Kernel (GFK) as a domain-adaptation transformer, integrated into KaleLinear’s public APIs and documentation.

Changes:

• Implements GFK with stable handling of near-zero principal angles.
• Adds kernel, transformation, validation, and public API tests.
• Documents GFK and adds an API map.

File	Description
tests/​transformer/​test_gfk.py	Tests GFK mathematics, behavior, and validation.
tests/​test_public_api.py	Checks the GFK public alias.
README.md	Introduces GFK, its reference, and the API map.
kalelinear/​transformer/​_gfk.py	Implements the GFK transformer.
kalelinear/​transformer/​__init__.py	Exports GFK.
kalelinear/​embed.py	Exposes GFK through the embedding API.
docs/​source/​usage.rst	Includes GFK in domain-adaptation usage.
docs/​source/​introduction.rst	Lists GFK among available transformers.
docs/​source/​api_transformers.rst	Adds GFK API documentation.
docs/​images/​api_map.svg	Adds a visual API overview.

_{Review effort: Balanced}