Fix IPA continuation: skip words with inline IPA, recover emptied cells

Three fixes:
1. fix_ipa_continuation_cell: when headword has inline IPA like
   "beat [bˈiːt] , beat, beaten", only generate IPA for uncovered
   words (beaten), not words already shown (beat). When bracket is
   at end like "the Highlands [ˈhaɪləndz]", return inline IPA directly.
2. Step 5d: recover garbled IPA from word_boxes when Step 5c emptied
   the cell text (e.g. "[n, nn]" → "").
3. Added 2 tests for inline IPA behavior (35 total).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

klausur-service/backend/tests/test_grid_editor_api.py

@@ -510,6 +510,23 @@ class TestGarbledIpaDetection:
         assert "klˈəʊs" in fixed   # close IPA
         assert "dˈaʊn" in fixed    # down IPA — must NOT be skipped
 
+    def test_continuation_skips_words_with_inline_ipa(self):
+        """'beat [bˈiːt] , beat, beaten' → continuation only for 'beaten'."""
+        fixed = fix_ipa_continuation_cell(
+            "[bi:tan]", "beat [bˈiːt] , beat, beaten", pronunciation="british",
+        )
+        # Should only have IPA for "beaten", NOT for "beat" (already inline)
+        assert "bˈiːtən" in fixed
+        assert fixed.count("bˈiːt") == 0 or fixed == "[bˈiːtən]"
+
+    def test_continuation_bracket_at_end_returns_inline(self):
+        """'the Highlands [ˈhaɪləndz]' → return inline IPA, not IPA for 'the'."""
+        fixed = fix_ipa_continuation_cell(
+            "'hailandz", "the Highlands [ˈhaɪləndz]", pronunciation="british",
+        )
+        assert fixed == "[ˈhaɪləndz]"
+        assert "ðə" not in fixed  # "the" must NOT get IPA
+
     def test_headword_with_brackets_not_continuation(self):
         """'employee [im'ploi:]' has a headword outside brackets → not garbled.