feat(llm-observability): AI explorer QB and builder_ai_query wiring (#12683)

#### Description

- Adds the `builder_ai_query` envelope type, seeded by the AI explorer
via `initialQueryAIWithType`.
- AI queries pull filter-bar keys from
`/api/v1/ai_observability/fields/keys` and values from
`/api/v1/ai_observability/fields/values`.
- `QuerySection` drops the builder's custom order-by (`ExplorerOrderBy`
via `renderOrderBy`) for the list and trace panels, along with
`showTraceOperator`. Ordering for those views is the list's own concern,
not the builder's — the trace view supplies its own control in #12688.
`limit` and `having` are now rendered disabled on every panel instead of
hidden on list.
- Hides the span-scope selector for AI queries — "Root / Entrypoint
Spans" ANDs badly with the gate, since GenAI attributes sit on nested
spans. Derived from the query itself, so no new prop on the shared
builder.
- `createNewBuilderQuery` inherits `builderQueryType` from the first
query, the way it already inherits `source`.
- Response conversion reads aggregation metadata from both builder
envelope types, not just `builder_query`.

TDD -
https://app.notion.com/p/signoz/Query-Builder-Changes-3b4fcc6bcd1980889c7aed782665e78d

#### Issues closed by this PR

Closes -
https://github.com/orgs/SigNoz/projects/39/views/20?pane=issue&itemId=226748421&issue=SigNoz%7Cengineering-pod%7C5889

#### Screenshots / Screen Recordings


https://github.com/user-attachments/assets/985cb178-ffb0-405c-b0a6-82ec242c3d68

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Co-authored-by: Gaurav Tewari <tewarig@users.noreply.github.com>