Implement i18n audit/localization cleanup and sync libstorm submodule

skills/nvgt-engine-dev/references/regression-checklist.md

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+# NVGT Regression Checklist
+
+Run this checklist after meaningful NVGT changes.
+
+## API/Source Verification
+- Verified changed API assumptions against NVGT primary sources.
+- For uncertain behavior, confirmed bindings in `<nvgt-root>/src/`.
+
+## Compile
+- Project compile command succeeds.
+- No new compile warnings/errors introduced.
+
+## Input/Navigation
+- Keyboard navigation works end-to-end.
+- Escape/close paths work from each UI/menu path.
+- No keyboard traps.
+
+## Screen Reader
+- New/changed controls announce meaningful labels.
+- Important events are announced consistently.
+- History/notification key paths still function if present.
+
+## Audio
+- Required sound paths resolve correctly.
+- Missing optional sounds fail gracefully.
+- Long-running loops do not leak/dangle sound handles.
+
+## Data Safety
+- File read/write failure paths are handled.
+- Save/load or serialization paths preserve prior behavior.
+- No accidental destructive behavior in migrations.
+
+## Reuse Boundary
+- Generic vs project-specific code separation is clear.
+- Extracted modules have minimal coupling.