one port announcement instead of sixteen, so a plugin can name itself

protocol.ts declared a separate SidecarEvent member per sidecar — music, vault,
slskd, headscale, transmission, invoiceshelf, jellyfin, photos, memos, gitea,
caldav, wallet, pty, email, notify, opencode — each an identical one-liner. Two
of them were for plugins that had already left the repository, which is the
tell: the platform was declaring event types on behalf of code it no longer
contains.

The cost was that a plugin could not announce its own port. `connection.send`
takes a SidecarEvent, so `{ type: 'notes:server', port }` did not typecheck
until someone added a line to the platform. A third-party plugin needed a pull
request against Officer before its sidecar would compile — for the one message
every HTTP sidecar has to send.

Now:

  export type SidecarPortAnnouncement = { type: `${string}:server`; port: number };

Nothing was lost at the point of use. The only consumer is
`sidecar.on(`${name}:server`, …)` in create-proxy.ts, which already cast to
read `.port`, because a handler typed `(event: SidecarEvent) => void` cannot
narrow from a computed template string.

The proof is a test that already existed: create-proxy.test.ts announces
`testcar:server` — a name never in the union — and now compiles without its
`as never`.

Removing the two casts that escaped the old type found something else. They
were not hiding union membership, they were hiding `port: number | undefined`:
Bun types Server.port as optional because a unix-socket server has none. So
`as SidecarEvent` on the whole object was suppressing a real nullability
warning, and would have suppressed a genuinely wrong event shape too. Replaced
with a narrow assertion on the port alone. Two further `as SidecarEvent` casts
in the same file turned out to be unnecessary altogether and are gone.

[open] The typo check is genuinely gone: a sidecar sending `muzik:server` while
its proxy listens for `music:server` now compiles, and the symptom is every
request answering 503 forever. The fix is not to restore the list — it is for
createSidecarConnector to announce the port itself from the `name` it already
holds, so the string is written once and the typo becomes unrepresentable.
Recorded in protocol.ts.

Verified live: officer and officer-music restarted, `[music] sidecar registered
on port 38803`, /api/music/manifest and /api/offscale/_health both 200.
tsgo clean, 797 tests, 787 pass, same 7.

src/servers/sidecar/create-proxy.test.ts

@@ -106,7 +106,7 @@ beforeAll(async () => {
 
   const proxy = createSidecarProxy({ name: 'testcar', prefix: '/api/testcar' });
   // What the registration socket would deliver when the sidecar reports its port.
-  handleSidecarMessage('test', { type: 'testcar:server', port: sidecar.port } as never);
+  handleSidecarMessage('test', { type: 'testcar:server', port: sidecar.port! });
 
   const protectedRouter = createRouter();
   protectedRouter.use(bodyParser());