The toolbar dock still showed the 🛡 emoji even after chrome.html learned
to render data-URI icons — because registerSidebarPanel({icon}) is the
per-panel icon that overrides manifest.icon, and Aegis was passing "🛡"
verbatim. Dropping the override lets addons-host's `icon = manifest.icon`
default kick in, so the dock button pulls the branded aegis.x/brand
shield the manifest now advertises.
Version bumped 0.4.1 → 0.4.3 to force seedBundledAddons to reseed the
new index.js on next launch.
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