* fix(cli): detach daemon from parent console on Windows
CREATE_NEW_PROCESS_GROUP alone leaves the daemon attached to the
parent console, so closing the launching cmd/PowerShell window fires
CTRL_CLOSE_EVENT down the inherited console and takes the daemon
with it. Add DETACHED_PROCESS so the child has no console at all;
stdout/stderr are already redirected to the log file before spawn.
* fix(cli): make `multica update` work while the binary is running on Windows
On Windows, a running .exe is opened without FILE_SHARE_WRITE, so the
previous os.Rename(tmp, exe) always failed with "Access is denied" —
every `multica update` on Windows hit this, because the CLI is
updating its own running binary.
Windows does allow renaming the running .exe (just not overwriting
it), so the new Windows-only replaceBinary moves the running binary
to `.old` first, installs the new one, and restores the original if
installation fails. A best-effort CleanupStaleUpdateArtifacts runs
at CLI/daemon startup to reclaim the leftover `.old` file once the
old process has exited.
Unix keeps the plain rename-over semantics (the old inode stays valid
for the running process).
* fix(cli): stop daemon via HTTP /shutdown instead of console ctrl events
With DETACHED_PROCESS the Windows daemon shares no console with the
stop caller, so `GenerateConsoleCtrlEvent(CTRL_BREAK_EVENT, pid)`
silently never reaches it — the old code would report "stop sent"
while the daemon kept running. Replace the platform-specific
stopDaemonProcess with a cross-platform POST to the daemon's HTTP
/shutdown endpoint, which cancels the same top-level context the
self-restart path already uses. Fall back to `process.Kill()` if
the HTTP call fails.
Also drops the now-unused stopDaemonProcess / CTRL_BREAK_EVENT
wiring, adds handler tests, and updates the DETACHED_PROCESS comment.
