Add CPU correctness gates + CI + Apache-2.0 license

[KoushikVGitHub]

Turns the repo's verified-by-hand claims into gates that run on every push, and makes the code legally reusable.

What's here

tests/ — 41 tests, CPU-only, ~11s, torch is the only dependency. No transformers, no video codecs, no CAMELS download, so it stays runnable on a bare runner.

File	Gate
test_distributed_sigreg.py	world=2 × batch-B ≡ world=1 × batch-2B over gloo on CPU — the twin of src/sigreg.py --verify (NCCL, 2 GPUs), which CI can't run. Plus a process-group-free check of the shard-additivity algebra the collective depends on.
test_anticollapse.py	The collapse_resolution.md finding as an executable claim: on a rank-2-of-64 batch whose per-dim std is a healthy 1.00, ‖∇sigreg‖ = 2.3e-4 vs ‖∇cov‖ = 0.25 (~1000×). Also pins the participation-ratio detector against known-rank inputs.
test_conv_stem.py	Pytest port of scripts/test_conv_stem.py (kept as the standalone demo): token-grid match, bit-identical linear path, legacy checkpoint keys, circular equivariance to 8e-7.
test_sigreg.py	~0 for N(0,I), large under collapse, penalizes mis-scaling, bit-reproducible under a seeded generator.
test_masking.py	Context/target partition disjoint + exhaustive, blocks contiguous, context never empty at the trained default.
test_jepa.py	Per-mode wiring: EMA teacher built only where needed, teacher frozen, stop_grad really severs the target, detectors in range.

CI — ubuntu-latest × py3.10/3.12 against the CPU torch wheel. The distributed gate is its own step because it's the load-bearing correctness claim.

LICENSE — Apache-2.0 (explicit patent grant). The repo is meant to be read and reused; without a license it was legally unusable.

Why these tests

Each targets a failure that does not raise. A broken all-reduce still trains. A non-circular pad still converges. A regularizer blind to dimensional collapse still logs a healthy loss — that one already cost a run, and eff_rank is the reason it was caught.

Note

One test skips on Windows (gloo cannot create a device there); it runs on the Linux matrix.