Use realpathSync to canonicalize paths before the plugin asset
boundary check, preventing symlink-based traversal bypasses that
could escape the plugin directory.
PluginTabContent now guards on plugin.enabled before mounting the
plugin module, and re-mounts when the enabled state changes so
toggling a plugin takes effect without a page reload.
PluginIcon safely handles a missing iconFile prop and skips
processing non-OK fetch responses instead of attempting to parse
error bodies as SVG.
Register 'plugins' as a known main tab so the settings router
preserves the tab on navigation.
