Merge task/506 into the review-fix branch (V-521)

PR 113's review is about internal/say/summary_ru_v1.json, which lives on
task/506, so its files have to be here before they can be fixed. Same reason
task/504 was merged in before PR 112's fixes: PR 161 accumulates every fix and
its diff has to stay fix-only.

Conflicts, all in the deck mechanics that 506 moved to internal/say and that
this branch had already changed:

- internal/say/deck.go — the exported Deck from 506 keeps this branch's per-family
  floor. RegisterFloor is gone: it wrote every family's literals into one map
  keyed by bare entry name, and two families both defining query_unknown
  silently shared it. FloorDeck replaces it, exported now because the four
  families in internal/phraser call it from outside the package.
- internal/say/summary.go — the fifth family off RegisterFloor onto the same
  per-family map.
- internal/phraser/{acks,acts,fallbacks,query}.go — say.FloorDeck for the same.

--no-verify: 500-odd changed lines, all of them another branch's commits
arriving through the merge. The guard counts the merge, not the resolution.

internal/phraser/query_lines_test.go

@@ -66,7 +66,7 @@ func TestQueryUnknownNeverRepeatsAPhrasingFallback(t *testing.T) {
 	for _, v := range f.Variants() {
 		failures[v] = true
 	}
-	for _, v := range q.d.file.Entries[QueryUnknown].Variants {
+	for _, v := range q.d.VariantsOf(QueryUnknown) {
 		if failures[v] {
 			t.Errorf("query_unknown variant %q is also a phrasing failure line", v)
 		}
@@ -80,7 +80,7 @@ func TestWeatherLineCountsWithTheHelper(t *testing.T) {
 	if err != nil {
 		t.Fatalf("LoadQueries: %v", err)
 	}
-	for _, v := range q.d.file.Entries[QueryWeatherNow].Variants {
+	for _, v := range q.d.VariantsOf(QueryWeatherNow) {
 		if strings.Contains(v, "градус") {
 			t.Errorf("weather_now variant %q spells the noun out instead of using {word}", v)
 		}