feat: add JSON output tests and README docs for analyze and status (#556)

* feat: add JSON output tests and README docs for analyze and status

Add 7 BATS tests covering `--json` output for `mo analyze` and `mo status`:
- schema structure
- field types
- pipe auto-detection.

Also document the `--json` flag in a new "Machine-Readable Output" README section, including the auto-detection behavior when piped.

* chore: use waitgroup go in status collector

---------

Co-authored-by: Tw93 <hitw93@gmail.com>

cmd/status/metrics.go

@@ -255,9 +255,7 @@ func (c *Collector) Collect() (MetricsSnapshot, error) {
 
 	// Helper to launch concurrent collection.
 	collect := func(fn func() error) {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
+		wg.Go(func() {
 			defer func() {
 				if r := recover(); r != nil {
 					errMu.Lock()
@@ -279,7 +277,7 @@ func (c *Collector) Collect() (MetricsSnapshot, error) {
 				}
 				errMu.Unlock()
 			}
-		}()
+		})
 	}
 
 	// Launch independent collection tasks.