@flue/opentelemetry drops tool error messages: empty exception.message and no span status message

[scubamaggo]

Describe the Bug

When a tool errors, @flue/opentelemetry (1.0.0-beta.3, with @flue/runtime
1.0.0-beta.9) produces an ERROR span that carries no error text anywhere:

1. exception.message is empty. The runtime's tool-end observation
   (type: 'tool') includes errorInfo: FlueErrorInfo, whose message field
   contains the real error text (populated by classifyError from the thrown
   Error). The tool-end handler ignores it: it builds the exception via
   errorMessage(event.result), and on error event.result is the
   model-facing content array ([{type: 'text', text: ...}]), which
   errorMessage (string / .message object only) cannot unwrap. So
   recordException fires with an empty message while the message sits unused
   in event.errorInfo.message.

2. The span status has no message. complete() calls
   span.setStatus({ code: SpanStatusCode.ERROR }) without a message.
   Trace UIs that render status.message (e.g. Arize Phoenix's spans-table
   "error" column) show nothing for error spans.

Expected Behavior

For an errored tool span, the exception event's exception.message should
contain errorInfo.message, and ideally the same text should be passed as
the message in setStatus, e.g. in the tool-end handler prefer
event.errorInfo?.message over deriving from event.result.

Steps to Reproduce

1. Create a basic flue app with the OpenTelemetry instrumentation registered
   (instrument(createOpenTelemetryInstrumentation({ content: { enabled: true, inline: true } })))
   and an InMemorySpanExporter on the tracer provider.
2. Register a tool whose execute throws:
   throw new Error('bridge timed out after 20s').
3. Run a conversation turn that calls the tool, then inspect the finished
   execute_tool span: span.status is { code: ERROR } with no message,
   and the recorded exception event has an empty exception.message —
   the text "bridge timed out after 20s" appears nowhere on the span, even
   though the tool-end observation's errorInfo.message contains it.