test: no shared conformance suite across runtimes

Many items in this project's issues are the same questions asked repeatedly: does this runtime propagate trace headers on its default HTTP client? Does it keep a span open for a streaming response? Does it report the right SDK name and runtime? Does double init do the same thing?

Each was found by reading one package and comparing to another. A table would have found them all at once, and would keep finding them.

**Work item.** Add a single matrix table to the repo (a test, or a generated doc) with one row per behavior and one column per runtime, covering at least:

| Behavior |
| -- |
| `sdk.name` and `sdk.packages` |
| `contexts.runtime.name` / `.version` |
| incoming server span: name, `sentry.op`, source |
| incoming server span: continues an inbound `sentry-trace` |
| outgoing default HTTP client: child span created |
| outgoing default HTTP client: `sentry-trace` + `baggage` sent |
| streaming response: span stays open until the body ends |
| streaming response: client cancel propagates upstream |
| request body capture honors `dataCollection.httpBodies` |
| `ignoreStatusCodes` drops the transaction |
| OPTIONS / HEAD produce no span |
| double `init()` behavior |
| tracing-off: tracing integrations absent |
| unhandled error in the handler is captured and rethrown |

Fill it from the existing per-runtime integration tests where they already exist, and let the empty cells drive the backlog. This is the item with the highest long-term return; every other item in this document is one cell in it.

**Prior art** Four open issues ask for more test coverage, but none of them for a cross-runtime behavior matrix:

* [#18635]()
* [#20874]()
* [#23610]()
* [#22523]()
* [#18635]() similar, but it is about running existing suites against more frameworks, not about asking every runtime the same behavioral question.

Comienza localizando las pruebas de integración existentes por runtime y las convenciones del repositorio para la documentación generada o las matrices de pruebas compartidas. Relaciona los comportamientos enumerados con la cobertura existente y, después, elige el formato de matriz compatible y completa sus resultados actuales. La tarea estará terminada cuando exista una tabla entre runtimes, con celdas vacías que identifiquen claramente la cobertura que falta y con las pruebas existentes reflejadas con precisión.

Escrito por el modelo de indexación a partir del texto del issue.