`serveUi({launch})`, `PluginLaunchTarget` and `makeLaunchHandler` (#129) are new API, so this is a
minor bump rather than a patch. It also carries `SyncError.message`, without which a host refusal
reaches a plugin's own UI as the bare tag `SyncError` and nothing else.
Unblocks rom-manager, whose main is currently RED: it merged the consuming change while still
pinning `^0.2.0`, so `bun install --frozen-lockfile` there resolves a kit without these exports and
the typecheck fails on all three. Publishing this and then bumping that pin is the fix — in that
order, because the lockfile cannot resolve 0.4.0 until it exists on the registry.
Tag `plugin-kit-v0.4.0` to publish; the workflow asserts the tag matches this version.