build: commit uv.lock — the locked universe CI now installs

#48 switched CI to 'uv sync --locked' but uv.lock was gitignored (an early
library-style choice; this repo is an application — the lock belongs in
git). Every run since failed at install: 'Unable to find lockfile'.
Un-ignore and commit the lock (217 packages, matches pyproject via
'uv lock --check'). CI now installs the exact universe local development
and all green verification ran against.

[Verification]: code tree byte-identical to the smoke-gated state
(175 passed); this commit adds a data file CI requires + one .gitignore
line removal.

.gitignore

@@ -15,7 +15,6 @@ workbench_data/*
 core-rs/target/
 core-rs/Cargo.lock
 
-uv.lock
 
 # Environment secrets — never commit real keys
 .env