feat(tasks): add inherited context and resilient LLM execution

Add read-only task context inheritance, ordered task-level LLM failover, live Worker controls, cascading task cleanup, FIFO task concurrency, cancellation diagnostics, UI updates, tests, build script, and changelog.

server/goals_test.go

@@ -0,0 +1,12 @@
+package server
+
+import (
+	"context"
+	"testing"
+)
+
+func TestCreateGoalsNilTask(t *testing.T) {
+	if got := (&Server{}).createGoals(context.Background(), nil, nil); len(got) != 0 {
+		t.Fatalf("nil task produced goals: %+v", got)
+	}
+}