Unified runtime registry for all query knobs, initialized at server startup. Consumes self-registering QueryKnob<T> descriptors, scans ServerParameterSet for parameters carrying query_knob annotations, matches each descriptor to its annotation, assigns dense indices, and builds the wire-name lookup map.

Each registry entry carries:

• QueryKnobBase* descriptor (for readGlobal, fromBSON)
• ServerParameter* (for write-path validate())
• wireName (for PQS wire-name lookup and explain output)
• pqsSettable flag
• applicability list
• minFcv

PQS-settable knobs get a StringMap<size_t> wire-name index entry. Non-PQS knobs get registry entries but no wire-name index entry. Initialization runs as a MONGO_INITIALIZER with prerequisite EndServerParameterRegistration. After init the registry is immutable. The core build logic accepts a ServerParameterSet& parameter so it can be unit-tested with synthetic parameters and annotations.

C++ unit tests with synthetic knobs, similar to how we test IDL server parameters in server_parameter_with_storage_test.cpp.