Harden module loading, cache introspection, and script flags

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What this task asks for

Harden ABS module resolution and caching, expose cache introspection APIs, and make module flags work correctly in script mode. Improve ABS module loading so `require()` remains deterministic across larger dependency graphs, supports discovery through `ABS_MODULE_PATH`, reports cache state, and handles module-related CLI flags in script mode. Equivalent paths that point to the same module file should reuse a single cache entry. A bare module name means a `require` target with no path separator and no file extension (for example `demo`); it resolves as `demo/index.abs`. Expose cache stats via `require_cache_info()` with numeric fields: `hits`, `misses`, `size`, and `inflight`. Expose cached module keys via `require_cache_keys()` as sorted canonical absolute paths. Expose `reset_require_cache()` to clear module cache and loader state.