fix: the API emitted undefined optionals as null, and the UI couldn't decode them (v0.3.2)

`Schema.optional(X)` means `X | undefined`, and the plain Schema encoder omits a
present-but-undefined key — but the HttpApi RESPONSE path serialises it as
`null`, which `X | undefined` then refuses when the client decodes it. Two
user-visible failures shipped in 0.3.1:

  - GET /api/status on a never-synced host returned `"lastSync":null`, so the
    Overview page could not decode its own status — i.e. every fresh install
    until the first successful sync.
  - POST /api/detect on a box with any emulator installed returned
    `"contested":null` / `"appId":null`, so the Emulators page's Detect button
    could not decode the result. It only looked fine because a value that has
    round-tripped through cache.json has those keys ABSENT rather than present
    -and-undefined, and absent keys encode correctly.

Nothing on this wire is `undefined` any more. EngineStatus.{lastSync,lastReport,
detectedAt} are `Schema.NullOr` and the engine sends explicit nulls. The
DetectedEmulator fields use `Schema.optional(Schema.NullOr(...))` instead —
tolerant of absent, undefined and null — because they also live in cache.json,
and requiring them would fail the whole cache decode on upgrade and silently
discard every art verdict.

plugin/test/wire.test.ts pins it: it drives the real makeApi handler stack
through toWebHandler and decodes the bytes with the shared contract schemas.
Against the old schema all five of its assertions fail; a unit test of either
side in isolation passes while the product is broken.

Also: the SSE feed now emits the current status on subscribe rather than only on
the next engine transition, so a freshly-opened console page is correct
immediately instead of stale until something happens.

plugin/package.json

@@ -1,9 +1,9 @@
 {
 	"name": "@punktfunk/plugin-rom-manager",
-	"version": "0.3.1",
+	"version": "0.3.2",
 	"private": false,
 	"type": "module",
-	"description": "Punktfunk plugin: scans ROM directories, maps them to emulators, and reconciles them into the host game library as a provider — with a console-hosted web UI. The reference plugin built on @punktfunk/plugin-kit.",
+	"description": "Punktfunk plugin: scans ROM directories, maps them to emulators, and reconciles them into the host game library as a provider \u2014 with a console-hosted web UI. The reference plugin built on @punktfunk/plugin-kit.",
 	"license": "MIT OR Apache-2.0",
 	"homepage": "https://git.unom.io/unom/punktfunk-plugin-rom-manager",
 	"repository": {