Adds a Hermes-backed sampling profiler API. Devs wrap critical paths
with Pionne.startProfile/stopProfile (or the Pionne.profile sugar);
the SDK enables Hermes' built-in sampler, dumps the trace as Chrome
Trace Event JSON, and ships it to POST /api/profiles. The server
keeps raw samples 7 days and aggregates nightly into P50/P95/P99 per
function x release for the dashboard's flame graph + cross-release
regression chart.

Overhead: ~1-3% CPU during capture, zero when idle. JSC no-ops
silently so app code stays engine-agnostic.

New types exported: ProfileMeta, ProfilePayload.