Close test-gap noise rows and sync coverage documentation.

Restore P1/P2/fleet/erasure COVERED rows in PROBLEMS.md with refreshed counts; drop fixed poll-duplication and Vitest-noise items. Silence ECONNREFUSED stderr in Vitest setup, alias download mock exports, and expand erasure/Path Tracer test coverage.

server/internal/erasure/store_test.go

@@ -0,0 +1,108 @@
+package erasure
+
+import (
+	"sync"
+	"testing"
+)
+
+func TestShardStorePutGetRoundTrip(t *testing.T) {
+	store := NewShardStore()
+	p := DefaultParams()
+	shards := [][]byte{[]byte("a"), []byte("b"), []byte("c"), []byte("d"), []byte("e"), []byte("f")}
+	store.Put("tok-1", p, shards)
+
+	got, ok := store.Get("tok-1", 2)
+	if !ok || string(got) != "c" {
+		t.Fatalf("get shard 2 = %q ok=%v", got, ok)
+	}
+	storedP, ok := store.ParamsFor("tok-1")
+	if !ok || storedP.DataShards != DefaultDataShards {
+		t.Fatalf("params=%+v ok=%v", storedP, ok)
+	}
+}
+
+func TestShardStoreGetReturnsCopy(t *testing.T) {
+	store := NewShardStore()
+	p := DefaultParams()
+	shards := [][]byte{[]byte("mutable")}
+	store.Put("tok-copy", p, shards)
+
+	got, ok := store.Get("tok-copy", 0)
+	if !ok {
+		t.Fatal("expected shard")
+	}
+	got[0] = 'X'
+	again, _ := store.Get("tok-copy", 0)
+	if again[0] == 'X' {
+		t.Fatal("Get should return defensive copy")
+	}
+}
+
+func TestShardStoreNilAndEmptyGuards(t *testing.T) {
+	var nilStore *ShardStore
+	nilStore.Put("x", DefaultParams(), [][]byte{[]byte("a")})
+	if _, ok := nilStore.Get("x", 0); ok {
+		t.Fatal("nil store should not serve shards")
+	}
+	if _, ok := nilStore.ParamsFor("x"); ok {
+		t.Fatal("nil store should not serve params")
+	}
+	nilStore.Delete("x")
+
+	store := NewShardStore()
+	store.Put("", DefaultParams(), [][]byte{[]byte("a")})
+	store.Put("empty-shards", DefaultParams(), nil)
+	if _, ok := store.Get("", 0); ok {
+		t.Fatal("empty token should not be stored")
+	}
+	if _, ok := store.Get("empty-shards", 0); ok {
+		t.Fatal("empty shard list should not be stored")
+	}
+	if _, ok := store.Get("missing", 0); ok {
+		t.Fatal("missing token should miss")
+	}
+	if _, ok := store.Get("missing", -1); ok {
+		t.Fatal("negative index should miss")
+	}
+}
+
+func TestShardStoreDelete(t *testing.T) {
+	store := NewShardStore()
+	p := DefaultParams()
+	store.Put("gone", p, [][]byte{[]byte("x")})
+	store.Delete("gone")
+	if _, ok := store.Get("gone", 0); ok {
+		t.Fatal("deleted token should miss")
+	}
+	if _, ok := store.ParamsFor("gone"); ok {
+		t.Fatal("deleted token params should miss")
+	}
+}
+
+func TestShardStoreConcurrentAccess(t *testing.T) {
+	store := NewShardStore()
+	p := DefaultParams()
+	payload := []byte("concurrent-erasure-store-payload")
+	shards, _, err := Encode(payload, p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	store.Put("concurrent", p, shards)
+
+	var wg sync.WaitGroup
+	for i := 0; i < 8; i++ {
+		wg.Add(1)
+		go func(idx int) {
+			defer wg.Done()
+			for j := 0; j < 50; j++ {
+				if _, ok := store.Get("concurrent", idx%len(shards)); !ok {
+					t.Errorf("worker %d miss on iter %d", idx, j)
+				}
+				if _, ok := store.ParamsFor("concurrent"); !ok {
+					t.Errorf("worker %d params miss", idx)
+				}
+			}
+		}(i)
+	}
+	wg.Wait()
+}