phraser: put the phrasing fallbacks in a versioned json (V-501)

Four lines he hears out loud lived as string literals in three Go files, so
rewording one meant a rebuild. They move to fallbacks_ru_v1.json on the shape
nudges_ru_v1.json already uses: embedded, schema-versioned, several variants,
never the same one twice running.

The gap phrase is marked fixed, because it names one specific missing model and
must not drift into a general "I do not know". Every accessor falls back to the
literal it replaced, including on a nil receiver: these strings exist because
something already failed, so a broken template file must not take her last
words away.

internal/phraser/fallbacks_ru_v1.json

@@ -0,0 +1,42 @@
+{
+  "schema_version": 1,
+  "name": "russian phrasing fallbacks v1",
+  "notes": [
+    "What she says when the model gave her nothing usable. Edit the wording here, no Go changes needed.",
+    "Rules: she is feminine about herself, he is a man addressed as ты. Never вы/вас/ваш, never plural imperatives, never он/его about him. No pet names.",
+    "These are heard after a failure, so they stay short and admit the gap. None of them may claim knowledge she does not have.",
+    "Placeholders: {sources} the notes or passages she was handed. A variant whose placeholder has no value is skipped, so every entry needs at least one variant with no placeholder — except query_sources, which exists only to read sources back.",
+    "fixed: true means exactly one variant and no picking. Used where the wording is load-bearing and must not drift between turns."
+  ],
+  "entries": {
+    "chat": {
+      "variants": [
+        "даже не знаю, что сказать.",
+        "не могу найти слов.",
+        "мысль ускользнула, повтори?",
+        "у меня сейчас пусто в голове."
+      ]
+    },
+    "query_unknown": {
+      "variants": [
+        "не знаю.",
+        "не знаю, честно.",
+        "тут я пас.",
+        "не скажу, не знаю."
+      ]
+    },
+    "query_sources": {
+      "variants": [
+        "вот что я нашла: {sources}",
+        "нашла вот это: {sources}",
+        "есть только это: {sources}"
+      ]
+    },
+    "world_gap": {
+      "fixed": true,
+      "variants": [
+        "сейчас не могу ответить — большая модель недоступна, а придумывать не хочу."
+      ]
+    }
+  }
+}