Family Runtime Selection

PR #1093 removed native runtime-strategy keys and their central registry. The runtime now selects exactly one family DSO from the format-1 bundle header.

{
  "format": 1,
  "family": "qwen",
  "task": "text_generation",
  "backend": "trt"
}

The loader opens libtrtmc_model_qwen.so, resolves its single trtmc_create_family factory, and verifies that the returned Task matches text_generation. Family-specific dispatch stays inside that DSO and is not a second public selection axis.

Concept	Current identity
Source/build/runtime owner	family
User-visible behavior	task and its abstract Task interface
Engine implementation	backend
Family-private pipeline variation	Family-owned bundle sections and code, not a registry key

To add behavior, edit the owning families/<family>/model.py, runtime/, and tests. To add another owner, add a complete family directory. The former runtime_strategy, task_strategy, registrar macros, central DSO index, and optimized-provider probe are not current extension points.