Fixes a correctness bug in google/adk-go where `RunAgentRequest.stateDelta` was accepted by `/api/run` but not applied, causing resumed runs to ignore caller-provided state updates.
Scattered source updates, isolated context, and manual follow-up across multiple feeds.
Added `applyStateDeltaIfPresent` and wired it into both `RunHandler` and `RunSSEHandler` so non-empty `stateDelta` is appended as a session event before agent execution, then merged into subsequent `Get()` state; includes a shallow-copy of the delta map to prevent request mutation from altering stored session event data.
Clients and operators using `/api/run` or `/api/run/sse` for resume workflows will now get expected session context updates before the agent starts, so reruns no longer silently proceed from stale state and recoverability improves for long-running conversations. The fix now records `stateDelta` as a session event through `sessionService.AppendEvent` before execution, and teams should watch for edge cases in event ordering and malformed/rapidly changing `stateDelta` payloads that could still affect merge behavior at high scale.
Clients and operators using `/api/run` or `/api/run/sse` for resume workflows will now get expected session context updates before the agent starts, so reruns no longer silently proceed from stale state and recoverability improves for long-running conversations. The fix now records `stateDelta` as a session event through `sessionService.AppendEvent` before execution, and teams should watch for edge cases in event ordering and malformed/rapidly changing `stateDelta` payloads that could still affect merge behavior at high scale.