fix(gitmost-bridge): нейтрализовать сплошные thematic breaks в транскрипте

Round-1 нейтрализация ловила только spaced-разделители (`- - -`),
но пропускала сплошные `---`/`***`/`___`: на git-sync round-trip такая
строка становится horizontalRule, а он не несёт текста — строка терялась
целиком (хуже list/quote-порчи). Символ `_` вообще отсутствовал в regexе.

GITMOST_MD_BLOCK_TRIGGER_RE дополнен альтернативой на целую строку-
thematic-break `([-*_])(?:\s*\1){2,}\s*$` (3+ одинаковых `-`/`*`/`_`,
solid или через пробел); прежние группы переведены в non-capturing,
чтобы `\1` ссылался на единственную capture-группу. Обе копии regexа
(bridge и pm-markdown тест) синхронны.

Тесты: bare `---`/`***`/`___` документированы как text-losing
horizontalRule; ZWSP-нейтрализованная форма round-trip'ится параграфом
с сохранённым текстом. Кейсы падают на старом regexе.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/editor/gitmost/gitmost-recording.test.ts

@@ -103,6 +103,9 @@ describe("gitmostInsertTranscriptIntoEditor", () => {
         "1. one",
         "> [!info] note",
         "```js",
+        "---", // solid thematic break -> horizontalRule (text-losing) if unneutralized
+        "***",
+        "___",
         "You: normal line",
       ].join("\n"),
     );
@@ -122,6 +125,9 @@ describe("gitmostInsertTranscriptIntoEditor", () => {
       ZWSP + "1. one",
       ZWSP + "> [!info] note",
       ZWSP + "```js",
+      ZWSP + "---",
+      ZWSP + "***",
+      ZWSP + "___",
       "You: normal line",
     ]);
 

apps/client/src/features/editor/gitmost/gitmost-recording.ts

@@ -253,11 +253,15 @@ const GITMOST_ZWSP = "​";
 // verbatim with NO block-escape (the pre-existing root cause), so a leading
 // `#`/`-`/`*`/`+`/`>`, an ordered-list `N.`/`N)`, a code fence ```/~~~, a table
 // `|`, or a `> [!info]` callout opener would silently become a heading / list /
-// quote / code block / table / callout. This matches a TRIMMED line's start;
-// the transcript's own `You:` / `Speaker N:` prefix begins with a letter and
-// never matches, so prefixed lines are left byte-exact.
+// quote / code block / table / callout. The final alternative matches a WHOLE-
+// LINE thematic break — solid `---`/`***`/`___` or spaced `- - -`/`_ _ _` (3+ of
+// the same `-`/`*`/`_`) — which round-trips into a `horizontalRule`; because
+// that node carries NO text, an un-neutralized separator line would LOSE its
+// text entirely (worse than the list/quote case). This matches a TRIMMED line's
+// start; the transcript's own `You:` / `Speaker N:` prefix begins with a letter
+// and never matches, so prefixed lines are left byte-exact.
 const GITMOST_MD_BLOCK_TRIGGER_RE =
-  /^(#{1,6}(\s|$)|[-*+](\s|$)|>|\d+[.)](\s|$)|```|~~~|\|)/;
+  /^(?:#{1,6}(?:\s|$)|[-*+](?:\s|$)|>|\d+[.)](?:\s|$)|```|~~~|\||([-*_])(?:\s*\1){2,}\s*$)/;
 
 // Append a transcript block BELOW the recording's audio node in a live editor:
 // a "Transcript" heading followed by one paragraph per non-empty transcript

packages/prosemirror-markdown/test/gitmost-transcript-neutralization.test.ts

@@ -29,7 +29,7 @@ const ZWSP = "​"; // U+200B
 
 // MUST stay in sync with GITMOST_MD_BLOCK_TRIGGER_RE in the client bridge.
 const MD_BLOCK_TRIGGER_RE =
-  /^(#{1,6}(\s|$)|[-*+](\s|$)|>|\d+[.)](\s|$)|```|~~~|\|)/;
+  /^(?:#{1,6}(?:\s|$)|[-*+](?:\s|$)|>|\d+[.)](?:\s|$)|```|~~~|\||([-*_])(?:\s*\1){2,}\s*$)/;
 
 const doc = (...nodes: any[]) => ({ type: "doc", content: nodes });
 const para = (t: string) => ({
@@ -57,6 +57,14 @@ describe("gitmost transcript neutralization (git-sync round-trip)", () => {
     "> [!info] note",
     "```js",
     "~~~",
+    // Solid + spaced thematic breaks — these re-parse into a `horizontalRule`,
+    // which carries NO text, so a bare separator line LOSES its text entirely
+    // (round-2 finding). `_` also only forms a block via this construct.
+    "---",
+    "***",
+    "___",
+    "- - -", // spaced dash break (solid form is caught by [-*+]\s too, but this is the break)
+    "_ _ _",
   ];
 
   it("BARE trigger lines corrupt into non-paragraph blocks (root cause)", async () => {
@@ -71,6 +79,18 @@ describe("gitmost transcript neutralization (git-sync round-trip)", () => {
     }
   });
 
+  it("BARE solid thematic breaks corrupt into a text-LOSING horizontalRule", async () => {
+    // The severe case: no text node survives. Documents why neutralization
+    // matters more here than for list/quote (where the text survived).
+    for (const line of ["---", "***", "___"]) {
+      const blocks = await roundtrip(line);
+      expect(blocks.map((b) => b.type)).toContain("horizontalRule");
+      // No block carries the original text anywhere.
+      const flat = JSON.stringify(blocks);
+      expect(flat).not.toContain(line);
+    }
+  });
+
   it("ZWSP-neutralized trigger lines round-trip as a single paragraph, text preserved", async () => {
     for (const line of triggerLines) {
       // The regex must actually classify each as a trigger.