Execute the Template Helpers Any Reduction RFC against current code

[lbliii]

Context

There is already a draft RFC for reducing Any in runtime helpers, but the current code has broader Any usage than the RFC's old counts and the work has not landed. This is a good bounded typing cleanup that strengthens refactoring safety without changing public behavior.

Evidence

• plan/rfc-template-helpers-any-reduction.md is still Status: Draft.
• A current scan shows 576 Any/dict[str, Any]/cast( matches under src/kida.
• Hotspots include src/kida/template/helpers.py, src/kida/template/render_helpers.py, src/kida/environment/core.py, and src/kida/compiler/partial_eval.py.
• The RFC's current-state counts are stale; for example, template/helpers.py now has many more Any usages than the four listed in the RFC.

Proposed Scope

• Refresh the RFC counts against current code.
• Land a narrow first PR focused on helper/filter/render-helper signatures where object or Protocols are clearly better than Any.
• Leave inherently dynamic template context APIs alone unless there is a clear type contract.

Done When

• The RFC is either updated and active, or closed with implemented work linked.
• A first bounded Any reduction lands with make ty clean.
• No runtime behavior changes are introduced.