Engine snapshot provenance and license exceptions

indexed_graph.py retains its original MIT header and separate MIT permissions.
uca_compiler.py and uca_estimation.py originally had no confirmed upstream
license declaration. On October 26, 2026, Yonghan Jung explicitly confirmed his
authority to license these bundled snapshots and authorized their public
distribution under the CausalEngine Noncommercial License 1.0 in the root LICENSE.
This present author authorization does not assert a historical upstream license
grant or a new MIT grant. The indexed_graph.py MIT permissions remain unchanged.

The current root LICENSE applies only to material Yonghan Jung is entitled to
license, subject to LICENSING.md. Prior valid MIT grants remain effective;
LICENSE-MIT.txt preserves their original text without regranting the entire
current package under MIT. Dependencies retain their own terms.

ENGINE_SOURCES.json sha256 values cover canonical package source files. Prior
pre-layout snapshot hashes and upstream_sha256 retain the original provenance.

2026-10-25 local uca_estimation.py patch: feature weights use exact normalized
minimum-L2 balance; finite weights retain the common-joint histogram/carrier
source law and its analytic full-indicator solution. Backward regression ridge
and source/evaluation splitting are unchanged. No upstream license is altered.

2026-10-26 local uca_estimation.py patch: point-score backward regressions use
XGBoost by default, including finite weight designs. Real-coordinate carriers
are auxiliary Gaussian proposals; support and finite-score moments are assumed.
Minimum-L2 weights and explicit finite/affine protocols are preserved. No
automatic causal interval or new upstream license permission is implied.

2026-10-26 local cleanup: backward fitting and one score-unit evaluation are
extracted into private helpers without changing random draw order. Paired
terminal-weight scores and shared-fit phase timings support a pilot comparison.
Weight mathematics, default learners and inference claims are unchanged.

2026-10-27 layout consolidation: the three engine modules now live directly in
src/causalengine, with package-relative imports identical to the former installed
payload. ENGINE_SOURCES.json records current hashes and preserves snapshot history.
No algorithm or licensing terms changed.
