portka-tools 1.8.0

Triage of #85 — video-bug-analyzer as an art/aesthetic-reference tool (mining a library of animated
GIF loops for palette + motion). video-bug-analyzer → 1.8.0 (repo-bootstrap and
app-website-evaluator stay 1.7.0, tab-chord-formatter 1.2.0). MINOR: two new analysis modes, both
built on existing plumbing, plus a framing tweak.

Added (video-bug-analyzer → 1.8.0, #85)

• --palette --over-time — the colour arc, not one flattened ramp. A seamless art loop often
  sweeps through very different colour states (powder-blue → magenta/cyan → back); a single dominant
  palette hides that. --over-time splits the clip into N windows (--segments, default 8) and prints
  each window's palette as t<sec> #hex #hex …, so the colour journey is visible. Reuses
  palettegen per window + the existing PPM swatch reader; honors --colors, --start/--end.
• --loop-check — is this a clean seamless loop? Reports the mean absolute pixel difference
  between the first and last frame (0 = identical wrap; <1% "loops cleanly", <4% near-seamless, else a
  visible seam) and writes a loopcheck.png strip (first │ last) so the seam is visible. Built on the
  PPM reader + the --strip hstack. Broadly useful to anyone making loops, GIFs, or shader toys.
• "Also useful for" framing (#85 item 5, echoing #14). The header/README/marketplace now call out
  the non-bug uses — art/colour reference, asset/QA — and that GIF input works on every mode, so
  the tool surfaces for an aesthetic-reference task, not just "bug/glitch/crash".

Deferred to IMPROVEMENTS.md

• --montage a.gif,b.gif,… — an N-way library survey (one representative tile per input), for
  eyeballing a whole collection at once (distinct from the pairwise --compare-videos).
• --palette (and --over-time) as an SVG/PNG swatch sheet artifact, not just hex text.

Pre-merge adversarial review hardening

A multi-agent review of the new ffmpeg/python code caught several real edge cases, all fixed:

• A window that decodes zero video frames no longer fabricates a stale palette (the -y fix
  wasn't enough — ffmpeg's image muxer opens lazily, so the prior window's file survived): the span
  is clamped to the video stream duration and win.ppm is removed before each window.
• A clip whose audio outlasts its video no longer sends --loop-check's tail seek into an
  audio-only region (a false "could not extract" error): both modes use the video stream
  duration, not format=duration.
• A 10-bit/HDR source (ffmpeg emits a 16-bit rgb48be PPM) is read correctly — -pix_fmt rgb24
  on frame grabs plus a parser that takes the high byte of each 16-bit sample — instead of garbage
  hex / a diff that ignores half the frame.
• A first/last frame size mismatch (a mid-clip resize) is reported as such rather than diffing
  misaligned pixels; a truncated/malformed PPM header no longer crashes the parser; --segments is
  capped at 200; and every ffmpeg write uses -y -nostdin.

Tests

• New coverage: --palette --over-time prints a per-window arc whose windows genuinely differ (a
  regression guard for the stale-frame bug); --loop-check calls a static clip a clean loop (+ writes
  the strip) and a hue-sweeping clip a seam; a clip whose audio outlasts its video survives both
  modes (no stale rows, no false error); --over-time without --palette exits 2; and both dry-runs
  print their commands. Suite: 217 passed, 0 failed, 1 skipped.