Extract shared _KeyedCache helper from CachedNodeNorm and CachedNameRes

[gaurav]

Background

src/babel_validation/services/nodenorm.py and src/babel_validation/services/nameres.py both implement identical cache structures:

• (query, frozenset(params.items())) tuple keys
• Parallel clear_curie / delete_query O(N) sweep methods
• Parallel from_url registries

This duplication means bug fixes or improvements to the cache logic must be applied in two places.

Proposed fix

Extract a small _KeyedCache helper (or a shared base class / mixin) in src/babel_validation/services/ that both CachedNodeNorm and CachedNameRes can reuse. Not blocking for the current PR, but worth cleaning up as the services layer grows.

Notes

• Identified during the Opus code review of PR Add GitHub issue tests #67.
• Not blocking; address in a follow-up refactor PR.