Phase 1 of #5963: reorganize building blocks (buffer, parser, input, data, and shared utilities) under common/primitives/. Runtime code (services, public API, CoreTerminal, InputHandler) stays in place. Update import paths across browser, headless, addons, and tests. Add TypeScript path mappings so common/* aliases resolve primitives first, then the common root. Co-authored-by: Daniel Imms <Tyriar@users.noreply.github.com>