Fix a fleet status board from three user bug reports

Challenge summary

Three user bug reports against one small Angular screen: a filter that narrows the wrong list, an empty state that never clears, and a button that fires twice.

What you'll practice

• Reproduce a bug from a user report before touching code.
• Derive filtered state from the source list instead of from a previous result.
• Spot duplicate event handlers created by form submit and click bindings.

What Premium unlocks

Premium unlocks the runnable Angular workspace, the three behavioral checks, the fixed solution and the root-cause walkthrough.