viser v0.6.1

Fixed

• HDR detection with ffprobe >= 8.0 — color_primaries and bits_per_raw_sample
  are no longer reported as top-level stream fields by ffprobe 8.x for HEVC/Matroska.
  hdr_kind() now falls back to the color_space field (bt2020nc, bt2020c) when
  color_primaries is absent, combined with pixel-format bit-depth detection.

Added

• Property-based tests (proptest) — randomised mathematical-invariant tests for
  convex hull (monotonicity, convexity, per-codec partitioning, below-hull containment)
  and ladder selection (bitrate/VMAF sorting, rung-count bounds, index contiguity).
• FFmpeg argument invariants — proptest-driven verification of encoder argument
  construction against FFmpeg's documented encoder syntax.
• FATE-style integration tests — 37 tests that generate synthetic test media via
  ffmpeg -f lavfi and exercise the full probe → encode → measure pipeline against
  real ffmpeg/ffprobe, validating resolution, codec, duration, bitrate monotonicity,
  VMAF scoring, progress reporting, segment extraction, and concatenation.
• just coverage / just coverage-lcov recipes and CI coverage job
  (cargo llvm-cov).