v6.6.2

Fixes

• Timestamps are no longer silently invalidated when options come from a tree
  root's .picopt.yaml instead of identical CLI flags: the config check now
  compares each tree's effective configuration, directory configs included.
• timestamps: true in a tree root's .picopt.yaml (e.g. written by -W -t)
  now enables timestamping for that tree without -t. CLI flags still win, and
  --dry-run / --list still disable stamping.
• Timestamp invalidation is now per tree and value-based: comment or formatting
  edits to .picopt.yaml files, rewriting them with -W, or running with a
  different set of top paths no longer invalidate stamps — only actual option
  changes do.
• Discarding stamps because the configuration changed now prints a warning
  naming the differing options instead of silently re-optimizing.
• Verbose timestamps, ignores, after, and memory budget summaries are no longer
  repeated once per directory when using per-directory .picopt.yaml files.

Migration note

• Existing timestamp files will mismatch once after this upgrade because the
  stored config changed shape. Either let the first timestamped run re-examine
  each tree once, or run once with -N (--timestamps-no-check-config) to keep
  the old stamps.