a plugin ships its own dock icon as a file, not a lucide name

The manifest's `icon` was a lucide NAME, resolved by `resolveIcon` — which
knows 106 glyphs out of lucide's ~1,500. A plugin naming one outside that set
silently rendered a neutral box, and a plugin from a marketplace had no way to
see the ceiling coming.

So the icon is a FILE now: `plugins/<name>/assets/icon.png`, discovered by
presence like everything else here. `manifest.icon` stays as an optional
fallback for a plugin with no artwork — example and offscale still use it — and
the file wins when both exist.

No new mechanism was needed. The app store already published sidecar assets:
`<dir>/assets/` → `public/plugins/<id>/`, served by a dynamic `/plugins/*`
route, with `DockItem.image` rendering an <img>. `pluginDockManifests()` simply
never emitted `image`. Install now publishes and uninstall unpublishes — the
one thing uninstall is allowed to delete, because these are copies whose
originals are still in the plugin's source.

Base64 in the manifest was considered and dropped. It would ride in every
/api/user/capabilities response for every user on every page load, can't be
cached separately, and puts a 5KB string literal in a source file — against the
rule this manifest keeps: what a directory listing can say, it says. It also
needs no support: `image` goes straight into <img src>, so a data: URL already
works for anyone who wants one.

Music ships OffMusic.png, resized 1254² → 256² (1.6MB → 108KB) with alpha
intact, sized for 3× DPI at the dock's 32px render. It also drops `icon` — the
artwork is a voxel duck in headphones, not a glyph.

The plugins page showed a generic Puzzle for every plugin; the list and detail
header now show the plugin's own icon when it has one.

Two bugs found while testing.

Dock.tsx imported 26 lucide icons and used 14. The twelve dead ones — Music,
Bitcoin, Receipt, Images, CalendarDays, Contact, Clapperboard, Mail, Network,
ArrowDownUp, FileText, FolderKanban, MonitorSmartphone — were residue from when
every feature had a hardcoded tile. Deleted.

And uninstalling a plugin left its icon URL answering 500, not 404. server.tsx
globs ./public at BOOT into one exact route per file, each holding a Bun.file
handle, spread into the route table AHEAD of the /plugins/* wildcard. So an
icon present at boot got an exact route that outlived the file, returning
ENOENT on every dock render with the error logged each time — exactly what the
wildcard's own comment says it exists to prevent. The comment covered the ADD
case; this is its mirror. `plugins/` is now excluded from the boot glob, so the
wildcard owns that prefix alone. Verified: 200 installed, 404 uninstalled, 200
reinstalled.

[open] A plugin's icon cannot be seen BEFORE installing it, which is the one
place an app store most wants to — assets are published at install by design,
and an authenticated icon route is no use to an <img>.

plugins/music/manifest.ts

@@ -10,6 +10,7 @@ import type { PluginManifest } from '@@/plugins/manifest';
 //   api/router.ts     the sidecar proxy, built here — thin, and it must never grow music knowledge
 //   cliamp/           the second playback path, parked
 //   widgets/          the dashboard widget, parked
+//   assets/icon.png   the dock tile, published to /plugins/music/ on install
 //   sidecar/          the whole /api/music contract: indexing, streaming, per-user state
 //   db/               music_favorites, _playlists, _playlist_items, _now_playing
 //   web/              the library panels; the shell renders the Workspace
@@ -44,7 +45,9 @@ export const manifest: PluginManifest = {
 
   label: 'Music',
   summary: 'The music library — browse, play, favourites and playlists',
-  icon: 'Music',
+  // No `icon` field: this plugin ships `assets/icon.png` and the file wins. A lucide name could only
+  // ever pick from the 106 glyphs the platform happens to bundle, which is a ceiling a plugin from a
+  // marketplace cannot see coming — and this one's artwork is a voxel duck in headphones, not a glyph.
   color: '#22c55e',
 
   // One permission gating the whole surface, grantable per role at read or write like every other.