Markless 0.3.1

A patch release with three fixes found while building the Markless docs site as
a Markless app on the published packages.

MDX islands that derive a value now resume

An MDX page is stitched from several .tsrx islands, and each island gets its
own symbol prefix. The view side already applied that prefix; the composed state
payload did not, so an island whose update re-derived a computed() looked up a
symbol the loader table did not know and failed with Unknown Markless MDX symbol. composeMdxState now prefixes deriveSymbolId the same way the view
side prefixes host and event symbol ids.

storage() works in router apps

A module-scope storage() used from a page or MDX island served a state payload
stamped as the storage version with no storage records, and the client refused
the whole payload, taking every island on the page down with it. Storage records
now travel through MDX composition, the payload version is computed from what the
payload carries, and MDX pages emit the no-flash storage seed script. A
storage() declared in document.tsrx used to be dropped silently; it now fails
the build with MARKLESS_ROUTER_DOCUMENT_STORAGE_UNSUPPORTED, which tells you to
move it into a component the page renders.

@for over a plain array renders its rows

@for over a collection that is not reactive state, such as an inline array, a
module constant, or an imported constant, rendered zero rows on the server with no
diagnostic. The compiler now carries the authored collection expression on the
repeat record and the server-render module evaluates it in the module's own
scope, so those loops render. A repeat with no readable collection is a build
error, MARKLESS_REPEAT_COLLECTION_UNREADABLE, instead of an empty list.