refactor(rr/core): tighten type hints; fix SkillbookView unwrap in search_skillbook

- recursive_agent: parametrize PydanticAgent[AgenticDeps, Any] generics
  so mypy resolves deps types; add `assert agent_run.result is not None`
  before unwrap to satisfy the static-type narrowing; format-only
  cleanup in `cache_read_tokens` line.
- rr/config: tighten `cache_ttl` from `str` to `Literal["5m", "1h"]`
  (the only values Anthropic accepts).
- rr/tools (search_skillbook): unwrap SkillbookView to its underlying
  Skillbook before calling `retrieve_top_k`, which expects the real
  type. Previously failed when invoked with a view.
- rr_step: declare `config: RRConfig` on the class so subclass-specific
  fields (cache_prompts, cache_ttl) are visible to type checkers; fix
  quote style on a string literal flagged by Black.