fix(agui): emit AG-UI interrupt for permission-type HITL tool confirmation (#2437) (#2495)

Fixes #2437.

The AG-UI adapter only surfaced **suspend-type** HITL (tools that throw
`ToolSuspendException` / frontend tools, i.e.
`GenerateReason.TOOL_SUSPENDED`). The **permission-type** HITL path was
dropped:

- Under `DEFAULT` permission mode, a non-readonly tool makes
`ReActAgent` emit `RequireUserConfirmEvent` +
`RequestStopEvent(PERMISSION_ASKING)`.
- `RequireUserConfirmEvent` had no converter, so it fell through to the
`RAW` fallback and **no `Interrupt` reached `RUN_FINISHED`**.
- The frontend therefore had nothing to confirm/deny, and resume was
impossible.

This builds directly on the converter-registry architecture introduced
in #2306, extending it to the confirmation path rather than changing its
design.