[eric] build: commit the lockfiles npm ci needs + ignore the build-info stamp

.gitignore

@@ -13,7 +13,9 @@ electron/dist/
 electron/python-env/
 electron/build-staging/
 electron/node_modules/
-electron/package-lock.json
+# electron/package-lock.json is intentionally COMMITTED (tracked): the build
+# runs `npm ci`, which needs the lockfile in-repo. Do not re-add this ignore.
+electron/build-info.json
 
 # Router is fetched from npm at build time into electron/build-staging/router.
 # No local router/ directory is tracked.

frontend/.gitignore

@@ -3,7 +3,9 @@ node_modules/
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
-package-lock.json
+# package-lock.json is intentionally COMMITTED: the build runs `npm ci`, which
+# refuses to run without a lockfile and installs it exactly. Ignoring it broke
+# clean/CI builds (no lock to ci from). Do not re-add this ignore.
 yarn.lock
 
 # Build outputs