PoseKit source-built MediaPipe candidate

Based on MediaPipe v0.10.35, commit
f8ef212d5c962c0e853db7e59d217056b187084b.

This is a locally modified build, not a Google-provided binary distribution.
Build changes include Apple build-rule alignment, explicit arm64 device and
simulator targets, C++-only OpenCV assembly, TensorFlow ICU conversion-data
linkage, Apple host-tool compatibility, zlib platform-guard compatibility,
and OpenCV SDK/build compatibility. Full patches accompany the build provenance.

All target C/C++ compilation defines GOOGLE_PROTOBUF_NO_RDTSC, selecting the
upstream protobuf map-seed fallback without a system-uptime read. OpenCV and
XNNPACK elapsed-time helpers remain. No pose algorithm or public bridge API
change is included in this candidate.

The bridge links source-built dependencies and retains required Objective-C
categories. The known proprietary prebuilt telemetry components are not included.
This statement does not replace runtime network validation or host-app review.

Original copyrights and license terms are retained in THIRD_PARTY_NOTICES.txt.
Eigen source availability is described in SOURCE_AVAILABILITY.txt. Model assets
are separate and are not covered by this dependency notice bundle.