v0.7.1

The new mark on the Marketplace listing, the README rewritten for 0.7.0,
and a false failure in the log fixed.

Changed

• The Marketplace icon, the README banner and the social preview carry a
  squiggled, handwritten blue "m" in the manner of Muse's own mark, in place of
  the plain "M" (at the owner's direction). It is drawn from a curve, not
  traced from Meta's mark.
• The README is rewritten for 0.7.0: a contents list, what is new, the
  limits, accessibility, the protected writes, and the corrections below.
• A file the Model API tools refuse as too large now says to read part of it
  with a shell command; it no longer suggests the search tool, which skips
  files over 1 MiB.
• Setting descriptions: attachOpenFile says it also hides the open-file
  chip and sends neither the file nor the selection when off;
  cleanupPeriodDays deletes when a window lists the conversations, not
  when it opens them; backend's auto falls back to Muse Code's sign-in
  when no key is stored.

Fixed

• npm run security:sast finds a semgrep that pip installed into Python's
  user Scripts folder when that folder is not on the shell's PATH (an
  editor started before it was added), instead of failing with "semgrep is
  not recognized".
• Resizing the sidebar while the prompt held a draft of several lines could
  log a false panel failure ("ResizeObserver loop completed with undelivered
  notifications"): the prompt refitted its height inside the browser's own
  resize callback. It now refits on the next frame.
• The UI harness's chips scenario had clicked a button renamed before the
  first release, so it never picked a file; it now uses the Attach menu.
• Four scenarios of the UI harness (filter, agents-off, usage-api,
  usage) had failed since M38, when a typed / stopped showing the
  palette's filter box, and the accessibility gate checked whatever the
  broken step left on screen. They open the palette from its button again,
  and a scenario that throws now fails the gate.