v0.6.7

Fixed

Two silent failures found while repairing a reordered course. Both share a shape
this project keeps meeting: a check that reports success about something it
never actually examined.

• export_web.py shipped 124 wrong-but-plausible figures under a green
  check. The fast path for embedded images only ever looked in <course>/figures/,
  while build_L1.py writes to <course>/_L1/figures/ — so on every course built
  by the batch pipeline it could not hit, and each embed fell through to a
  recursive walk that indexes the whole work dir by basename. After a manifest
  reorder there are two generations of cNN_frame_XXXX.jpg on disk (old numbering
  left in _L1/_stale_figures/, new in _L1/figures/), so one basename means two
  different pictures. The resolver picked one — silently when segment context
  happened to scope it — and embed-check: all N image embeds mapped + copied ✓
  reported success. Captions were right; 124 of 896 images were not.
  Now: figure roots are an ordered list (figures/, then _L1/figures/);
  candidates are collapsed by content hash, so identical bytes under several paths
  are not an ambiguity; a genuinely ambiguous basename is an error that fails the
  export, and one resolved by segment context prints a warning instead of
  resolving silently. Stage the intended generation in <course>/figures/ to pin it.
• audit_segmentation.py judged delivered courses by a superseded artifact.
  It read only proposal.md — a planning note — and never segments.json, which
  is what actually ships. Every reordered course therefore returned REGENERATE,
  including one whose 20 segments each still mapped to a contiguous block of the
  corrected order and needed nothing but a display_order fix; acting on that
  verdict would have rewritten 41 L2/L3 notes for no reason. It now checks the
  delivered segmentation first — contiguity (is the grouping intact?), coverage
  (does any clip belong to no segment?), and whether playback order follows real
  time — and downgrades proposal staleness to INFO when that segmentation holds up.
  Overlapping source pairs already sitting in one segment are reported as intended,
  not as a defect to fix.