feat(trace): add advanced span filters - #2466

Add `filters` to `Trace.getSpans()` so callers can select spans by type,
name, error state, partial metadata, and duration without fetching the
whole trace and filtering it themselves.

```typescript
const spans = await trace.getSpans({
  filters: {
    spanType: ["tool"],
    name: ["search", "lookup"],
    hasError: true,
    metadata: { model: "gpt-5" },
    duration: { min: 0.5, max: 10 },
  },
});
```

Combine filter dimensions with AND and match any value within each name
or span-type list. Duration bounds are inclusive and measured in seconds.
Keep the existing top-level `spanType` option supported.

Apply consistent filtering to buffered spans, complete trace caches, and
BTQL queries. Validate metadata as cycle-free JSON data, check returned
metadata candidates locally to avoid backend type coercion, and avoid
caching partial filtered results as complete traces.