Apply preset defaults without a Babel API

[OskarEichler]

Summary:

The preset's Babel-API accesses are optional, but invoking it without the Babel API still has two incomplete fallback paths: preset() can read properties from an undefined options object, and getPreset(code, {dev: false}) receives no transform profile and silently falls back to legacy class transforms instead of the normal hermes-stable default.

Default options to an empty object, consistently rely on that non-null invariant throughout the configuration builder, and apply hermes-stable when neither explicit options nor babel.caller provides a profile. Explicit options and caller-provided profiles retain precedence.

Changelog:

[GENERAL] [FIXED] - Apply normal preset defaults when invoked without a Babel API or options object.

Test Plan:

• Added a regression proving preset() builds without options or a Babel API.
• Added a transform regression proving no-API invocation preserves classes under the default hermes-stable profile; exact baseline lowers the class to helpers.
• Full preset Jest passes: 4/4 suites, 112/112 tests, 16 snapshots.
• Fresh Flow check reports 0 errors.
• Targeted no-ignore ESLint, Prettier, and git diff --check pass.

No breaking change: explicit profiles/caller behavior are unchanged, while standalone invocation now matches the preset's documented default path.