feat(bot): Коммит — создание, замена и удаление файлов, черновик

- новый файл: имя → содержимое текстом (```-обёртка снимается) или документом
- новая папка (виртуальная, пока в ней нет файлов), замена с diff +N/−M, удаление
- валидация: имя, ≤ 100 КБ, UTF-8, без NUL; .py — ast.parse с выбором «исправить / всё равно»;
  .sourcecraft/, .tgit/, ruff.toml из бота не меняются
- DraftService: черновик в БД, 24 ч, ≤ 50 изменений; удаление нового файла убирает его из черновика
- дерево показывает черновик поверх репозитория: 🆕 / ✏️ / 🗑, размер — как будет после пуша
- экран черновика (A/M/D) с «↩️ убрать»

Refs #26

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/repo/test_drafts.py

@@ -0,0 +1,72 @@
+from datetime import UTC, datetime, timedelta
+
+import pytest
+
+from app.db.models import ChangeOp, User
+from app.db.session import SessionMaker
+from app.repo.drafts import MAX_CHANGES, DraftFull, DraftService
+
+UID = 7
+SHA = "a" * 40
+
+
+class Clock:
+    now = datetime(2026, 10, 15, tzinfo=UTC)
+
+    def __call__(self) -> datetime:
+        return self.now
+
+
+@pytest.fixture
+async def svc(sessions: SessionMaker) -> DraftService:
+    async with sessions.begin() as s:
+        s.add(User(tg_id=UID, full_name="u"))
+    return DraftService(sessions, clock=Clock())
+
+
+async def test_put_get_and_order(svc: DraftService) -> None:
+    await svc.put(UID, SHA, "b.py", ChangeOp.ADD, b"b")
+    await svc.put(UID, "other-sha", "a.py", ChangeOp.MODIFY, b"a")
+
+    draft = await svc.get(UID)
+    assert draft is not None and draft.base_sha == SHA  # base fixed when the draft started
+    assert [(c.path, c.op) for c in draft.changes] == [("b.py", ChangeOp.ADD), ("a.py", ChangeOp.MODIFY)]
+
+
+async def test_editing_a_new_file_keeps_it_added_and_deleting_it_drops_it(svc: DraftService) -> None:
+    await svc.put(UID, SHA, "n.py", ChangeOp.ADD, b"1")
+    await svc.put(UID, SHA, "n.py", ChangeOp.MODIFY, b"2")
+    draft = await svc.get(UID)
+    assert draft is not None and draft.changes[0].op is ChangeOp.ADD and draft.changes[0].content == b"2"
+
+    await svc.put(UID, SHA, "n.py", ChangeOp.DELETE, None)
+    draft = await svc.get(UID)
+    assert draft is not None and draft.changes == []
+
+
+async def test_drop_message_clear(svc: DraftService) -> None:
+    await svc.put(UID, SHA, "a.py", ChangeOp.ADD, b"1")
+    await svc.put(UID, SHA, "b.py", ChangeOp.DELETE, None)
+    await svc.drop(UID, "a.py")
+    await svc.set_message(UID, "feat: x")
+
+    draft = await svc.get(UID)
+    assert draft is not None and [c.path for c in draft.changes] == ["b.py"] and draft.message == "feat: x"
+    await svc.clear(UID)
+    assert await svc.get(UID) is None
+
+
+async def test_expired_draft_is_gone(svc: DraftService) -> None:
+    await svc.put(UID, SHA, "a.py", ChangeOp.ADD, b"1")
+    Clock.now += timedelta(hours=25)
+    try:
+        assert await svc.get(UID) is None
+    finally:
+        Clock.now -= timedelta(hours=25)
+
+
+async def test_draft_size_limit(svc: DraftService) -> None:
+    for i in range(MAX_CHANGES):
+        await svc.put(UID, SHA, f"f{i}.py", ChangeOp.ADD, b"")
+    with pytest.raises(DraftFull):
+        await svc.put(UID, SHA, "one-more.py", ChangeOp.ADD, b"")