F7 gains an Authorship mode (segmented header toggle) that renders the current doc
with each span colored by its F3 author (Claude blue / human green), inline and
char-precise via PUA sentinel injection; code/mermaid fences get a block-level
author badge. Baseline-independent (INV-26), reads AttributionController.spansFor.
INV-26..28. Surfaced as friction during F8 testing.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Ben Stull