Use key presence check instead of OptionalParam in UI gate

Check for the "state" key directly in the args map rather than using
OptionalParam and ignoring its error. This ensures that a wrongly-typed
state value bypasses the UI form (falling through to the normal
validation path) instead of silently showing the form.

Co-authored-by: mattdholloway <918573+mattdholloway@users.noreply.github.com>

Author: Copilot

pkg/github/issues.go

@@ -1083,8 +1083,7 @@ Options are:
 					// Skip the UI form when a state change is requested because
 					// the form only handles title/body editing and would lose the
 					// state transition (e.g. closing or reopening the issue).
-					state, _ := OptionalParam[string](args, "state")
-					if state == "" {
+					if _, hasState := args["state"]; !hasState {
 						issueNumber, numErr := RequiredInt(args, "issue_number")
 						if numErr != nil {
 							return utils.NewToolResultError("issue_number is required for update method"), nil, nil