refactor(static-config): distinguish not-analyzable from field-absent

resolve_static_config now returns Option<FxHashMap<..., StaticFieldValue>>:
- None: config is not analyzable (no file, parse error, no export default,
  or exported value is not an object literal) — caller should fall back to NAPI
- Some(map): config was successfully analyzed
  - Json(value): field extracted as pure JSON
  - NonStatic: field exists but value is not a JSON literal
  - key absent: field does not exist in the config

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: branchseer