Fix the simulation gateway's 81 Pyright errors #865

Problem

The simulation gateway has 81 Pyright errors, tolerated by rules/baselines/pyright-gateway.txt under sim.quality.pyright-gateway (added in #864):

• 66 possibly-unbound variables and 6 "must return value on all code paths" errors in endpoints.py. Each comes from with runtime.span(...): policyengine-observability annotates its scope managers' __exit__ as returning bool, so Pyright assumes a span may swallow the exception raised in its block.
• 7 argument-type errors in endpoints.py: the budget-window submit response's status, and the VersionRoutingState TypedDict that callers and helpers both treat as a plain dict.
• 2 attribute-access errors in smoke_app.py, where hasattr(route, "methods") doesn't narrow Starlette's BaseRoute.

Proposal

Fix all 81 without changing behaviour, shrinking the gateway's baseline in each commit until it is empty. Open spans with scopes.span(runtime, ...) from #864, and correct the two annotations and the route narrowing.