add `state` to various requests

[WiggidyW]

needed for:

• agent completions
• vector completions
• function executions

state will be per-upstream, e.g. Openrouter and Claude Agent SDK have different state types

the way this will work for vector completions is any agent that isn't of the same upstream will error out, so it'll go through the fallbacks looking for one and if none are of that upstream then that agent will fail, but vector completions are fault tolerant so it doesn't matter

for function executions, we'll need to thread state from the request down to every vector completion

this blocks the builder simulations. It's important that the builder using ObjectiveAI judgment is able to clone its memory into the judgment harness when it executes judgment functions

[WiggidyW]

un-marking this as a blocker