Rebind metric instruments when the provider changes

Metric instruments can retain a no-op provider after startup

If metric instruments are created before the real global provider is registered, check whether the SDK upgrades those existing handles. Where it does not, starting export later leaves application counters silent. Resolve instruments against the current provider and recreate the cached set when provider identity changes. Test import and recording before startup, then assert successive exports contain advancing counters and histogram buckets. Mocked instruments alone cannot exercise this lifecycle. Pre-start measurements remain discarded unless buffering is explicitly implemented; reproducing this hazard locally does not establish that production uses the same import order.

Applies when: Metric helpers can load or execute before telemetry startup. Keywords: metrics startup initialization no-op provider instruments counters export lifecycle