Adds contract-focused regression coverage for the Electron HTTP server,
remote-control events, settings events, and managed download paths, and makes
Tier A coverage fail closed when instrumentation fails or a runtime-owning
production file disappears from a project or from the merged Istanbul report.
The old `coverage:ci` exited 0 despite a `Failed to collect coverage`
diagnostic: libs/m3u-state/src/lib/effects.ts was simply absent from the merged
map. All 30 Tier A reports are now required, the merged map covers 710 files,
and effects.ts is reported as 0/159 instead of silently disappearing.
Also fixes remote static-file path containment for encoded, malformed, NUL,
POSIX and Win32-style traversal inputs, with behavior-preserving testability
seams.
Statements 69.27% -> 69.54%; http-server.ts 0% -> 90.21%,
remote-control.events.ts 0% -> 96.55%, settings.events.ts 59.25% -> 96.29%.
4gray