Full type checking pyright coverage

[aabmass]

Adding type annotations and getting pyright passing is not in scope for migrated OpenInference libs. The skill we use tells the agent to opt the package out of pyright checking.

This is good for the initial pass, but it would be much better to have static coverage for instrumentations, and required any new code to pass type checking.

Originally posted by @lmolkova in #143 (comment)

[bhumikadangayach]

Hey @aabmass, I can pick this up.
Heads up — #153 already closed most of #41 (removing Any from the invocation classes), except the dataclass fields in types.py, which were called out as out of scope there. So, util-genai's types.py seems like the obvious starting point, and it'd close #41 fully too.
Before I touch anything else — do you want Pyright gating new code from day one with existing files exempted (# pyright: ignore or a per-file allowlist), and we burn that down package by package? Or strict mode required everywhere immediately?
I'll open a small PR for util-genai/types.py first either way, just want to agree on the exemption strategy before doing the rest of the packages.

[bhumikadangayach]

Hey @aabmass, just following up on the gating strategy question above (gate-new-code vs. strict-everywhere) — no rush, but happy to go with whichever you prefer. If it's easier, I can default to gate-new-code (seems like the more common convention) and start on util-genai/types.py unless you'd rather I wait for your input.