OmniGlyph 1.3.1

Docs-only. Syncs the npm package page with the corrected 1.3.0 documentation
(the 1.3.0 tarball was cut from the version-bump commit, before these edits).
No change to the compression path, billing math, or any shipped behavior.

Docs

• docs: the Grok changelog entry now describes the net shipped profile
  (stock 5×8 white AA + in-image IDS), not the 9×12 cell that never shipped in
  a tagged release; the universal IDS block, the 64 → 96 fact-sheet budget, and
  the residual-height gate are split into their own feat(render) entry; the
  two $0 eval harnesses (eval/grok-density, eval/ab/guards-3arm) are
  logged. The README gains an Opt-in flags note for OMNIGLYPH_GUARD_SECRETS,
  OMNIGLYPH_KEEP_SYSTEM_TEXT, and the fail-closed Grok opt-in.