v0.2.1

Experimental 0.x release. Provider/device E2E acceptance remains; see README and docs/acceptance.md.

• Preserve ICE URI total-deadline timeout classification when timer callbacks are
  delayed behind a per-address timeout; distinguish exhausted server attempts in tests.

• Fix RTCP PLI throttle validation to compare only within the valid observation
  window, and cover deliberately delayed observers in the normal and NativeAOT suites.

• Version 0.2.0 was not published: its release validation hit this scheduling-sensitive
  test assertion. The original tag is preserved; 0.2.1 also includes the ICE deadline fix above.

• Add opt-in, bounded versioned packet-stage diagnostics with live attachment,
  sampling, expiry, cancellation, queue/drop attribution and consumer-owned .NET
  Meter/Activity publication outside media loops.

• Trace host/TURN UDP/TCP/TLS receive boundaries, secure receive/audio queues and
  audio/video send locks, protection and local send completion; preserve explicit
  unknown kernel/TLS/socket timing and caller-owned pacing.

• Expose non-mutating per-source RFC 3550 reception snapshots, remote reception
  reports about transmitted streams, RTT age/staleness and route/consent evidence.

• Add deterministic local fault/lifecycle/collector tests, NativeAOT execution and
  measured paced-Opus allocation/CPU/delivery reports. See diagnostics
  and release measurements.

Full Changelog: v0.2.0...v0.2.1