MainSequence Desktop 0.4.13 preview

Fixes MainSequence MCP and agent tools being refused as "no longer connected" after
/reload-plugins, and the header offering Sign in while already signed in.

Claude Desktop hosts the engine through the SDK, so session.start, including the one a
plugin reload raises, can name no drawing surface. Startup (workspace preferences,
session check, environments and MCP tool registration) was gated on that surface and
did not run until a pane section was opened. Startup now runs when the session reports
a desktop surface, on the first desktop footer, composer-band or pane draw, or when the
model calls a MainSequence tool before any of those; that call waits for registration
instead of being refused. Startup still runs once per session, and terminal or headless
sessions spawn nothing.

Validation: 88 Node tests, nine native Desktop simulator tests and loader validation
passed. A real end-to-end run of the installed plugin hooks with the real worker and
local backend held a two-turn conversation with Back Office Helper, called the Back
Office get_current_user MCP tool, listed the MCPs and tools, and drew the Tutorial
Helper icon in the list, details, composer band and tool rows. Desktop's bundled Code
2.1.299 engine replayed those responses, including a model call to the Back Office tool
immediately after a reload with no surface.

Bundles devtools 0.2.8. Update from the MainSequence marketplace and reload the plugin
in the Code chat. Node 22+ required.

Source revision: 43231f9. Archive SHA-256: 43dbda80f541d3a687a79730bf7b61fa716eac3776872d447954922a5a399085.