* test(native): cover the desktop MCP server lifecycle
`tests/e2e/native/**` had no MCP coverage, so nothing verified that the
real Tauri shell finds and spawns a server. Browser E2E cannot: the spawn
path short-circuits to the Vite-managed server in development.
Add a native spec that asserts what the app actually resolved: a missing
install reports its own reason, a resolvable binary either becomes healthy
with a discovery file and answering port or is refused with a version
explanation, and hiding the resolved binary then reports the missing
install without relaunching.
Also generate the desktop icons in `build:native-test`, since they are
ignored and the build failed on a clean checkout, and let the snapping
spec select its own section instead of assuming the dialog state.
* test(native): resolve the home directory portably
process.env.HOME is unset on Windows, which put the discovery override
outside the home directory. The app accepts a server-reported discovery
path only inside it, so it fell back to its own path and could not read
the test server's token.
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