fix(plugins): give installed plugins the same enable toggle as bundled ones

[kipavy]

The bug

Whether a plugin could be disabled depended on how it reached the disk, not on what it is.

The Installed tab builds its first list from seededPluginManifests(externalPluginIds), which despite the name returns every loaded plugin that isn't in installedMeta — i.e. the app-bundled ones. Only those rows rendered a <Toggle>. Rows built from installedMeta — anything installed from a catalogue, a URL, or a local scan — rendered Update / Reload / Uninstall and no toggle.

Consequences:

• Installing a first-party plugin from Browse instead of using the bundled copy moved its id into installedMeta, so loadSeededPlugins then skipped it and it appeared in the external list — the same plugin, silently losing the toggle it had while bundled.
• Themes, which are only ever installed, never had one at all.

The fix

The rule becomes a property of the plugin rather than of its provenance, in one place both row types call:

function EnableToggle({ manifest, enabled, onToggle }) {
  const themeOnly = manifest.permissions.length === 1 && manifest.permissions[0] === "themes";
  if (themeOnly) return null;
  return <Toggle checked={enabled} onChange={() => onToggle(manifest.id, enabled)} />;
}

A theme-only plugin contributes nothing but themes, so "disabled" and "not installed" would mean the same thing to the user — it stays installed-or-not, which is the behaviour that was already there and worth keeping. Everything else can be turned off without losing it, bundled or installed.

Installed rows compute enabled as isLoaded && isEnabled(meta.id, true), mirroring externalPluginActive from #181, and now dim when disabled the way bundled rows already did.

Tests

PluginsSection.enableToggle.test.tsx — five tests covering the matrix (non-theme installed / non-theme bundled / theme installed / theme bundled) plus one that the toggle actually deactivates the plugin and persists the override.

Written first; three failed for the expected reasons: installed non-theme had no toggle, bundled theme had one it shouldn't, and there was nothing to click. 16 tests across the three PluginsSection files pass now, tsc --noEmit clean.

Live verification

In the headless container on this branch, both installed from the live catalogue:

Installed row	Toggle
SSH Config Sync	yes
Emerald Night	no

Toggling SSH Config Sync off flips aria-checked to false, dims the row to opacity: 0.7, and survives a restart — the override persists and #181's boot path honours it. Toggling back on restores it.

Negative control: reverting just this commit's change to PluginsSection.tsx in the same running build drops SSH Config Sync's toggle count from 1 to 0; restoring brings it back.

Note

seededPluginManifests is misleadingly named — it returns loaded-minus-installed, not "seeded". It misled me into an incorrect claim earlier in this work. Renaming it is not in this PR, but it should probably be unmanagedPluginManifests or similar.