Standardize daemon detection with tryDaemonLock probe (bd-wgu4)

- Extract lock checking to internal/lockfile package
- Add lock probe in RPC client before connection attempts
- Update daemon discovery to use lock probe
- Eliminates unnecessary connection attempts when socket missing

Closes bd-wgu4

Amp-Thread-ID: https://ampcode.com/threads/T-3b863f21-3af4-49d3-9214-477d904b80fe
Co-authored-by: Amp <amp@ampcode.com>

internal/lockfile/process_windows.go

@@ -0,0 +1,25 @@
+//go:build windows
+
+package lockfile
+
+import (
+	"golang.org/x/sys/windows"
+)
+
+const stillActive = 259
+
+// isProcessRunning checks if a process with the given PID is running
+func isProcessRunning(pid int) bool {
+	handle, err := windows.OpenProcess(windows.PROCESS_QUERY_LIMITED_INFORMATION, false, uint32(pid))
+	if err != nil {
+		return false
+	}
+	defer windows.CloseHandle(handle)
+
+	var code uint32
+	if err := windows.GetExitCodeProcess(handle, &code); err != nil {
+		return false
+	}
+
+	return code == stillActive
+}