feat(inbox): docx table cells + grouped pptx shapes (stage 2g)

Two structural regions the office extractors missed, no new dependency:
- .docx table cells (they live outside doc.paragraphs);
- grouped .pptx shapes (add_group_shape moves a shape inside the group, so the
  extractor recurses through MSO_SHAPE_TYPE.GROUP to reach it).

Each proven by an injection-in-region REJECT plus a clean-region ADMIT. Tests
310 -> 314.

tests/test_okf_inbox_uploads.py

@@ -363,3 +363,62 @@ def test_pptx_notes_detach_proof(tmp_path):
     fp = _make_pptx(tmp_path, body="A routine slide.")
     _extracted, _result, verdict = receive([fp])
     assert verdict == "ADMIT"
+
+
+# --- slice 2g: office-extractor completeness (no new dep) -------------------
+# Two structural regions the earlier slices did not reach: .docx table cells (they
+# live outside doc.paragraphs) and grouped .pptx shapes (add_group_shape moves the
+# shape inside the group, so only recursion reaches it).
+
+
+def _docx_with_table(tmp_path, cell_text, name="table.docx"):
+    from docx import Document
+
+    d = Document()
+    d.add_paragraph("A normal paragraph.")
+    table = d.add_table(rows=1, cols=2)
+    table.cell(0, 0).text = "label"
+    table.cell(0, 1).text = cell_text
+    fp = tmp_path / name
+    d.save(str(fp))
+    return fp
+
+
+def _pptx_with_grouped_text(tmp_path, text, name="grouped.pptx"):
+    from pptx import Presentation
+    from pptx.util import Emu
+
+    prs = Presentation()
+    slide = prs.slides.add_slide(prs.slide_layouts[6])
+    tb = slide.shapes.add_textbox(Emu(0), Emu(0), Emu(1000000), Emu(400000))
+    tb.text_frame.text = text
+    slide.shapes.add_group_shape([tb])   # moves tb inside the group (not top-level)
+    fp = tmp_path / name
+    prs.save(str(fp))
+    return fp
+
+
+def test_docx_table_cell_injection_is_caught(tmp_path):
+    fp = _docx_with_table(tmp_path, _INJECTION)
+    _extracted, result, verdict = receive([fp])
+    assert result.disposition is Disposition.FAIL_SECURE
+    assert verdict == "REJECT"
+
+
+def test_clean_docx_table_admits(tmp_path):
+    fp = _docx_with_table(tmp_path, "a clean value")
+    _extracted, _result, verdict = receive([fp])
+    assert verdict == "ADMIT"
+
+
+def test_pptx_grouped_shape_injection_is_caught(tmp_path):
+    fp = _pptx_with_grouped_text(tmp_path, _INJECTION)
+    _extracted, result, verdict = receive([fp])
+    assert result.disposition is Disposition.FAIL_SECURE
+    assert verdict == "REJECT"
+
+
+def test_clean_pptx_grouped_shape_admits(tmp_path):
+    fp = _pptx_with_grouped_text(tmp_path, "clean grouped text")
+    _extracted, _result, verdict = receive([fp])
+    assert verdict == "ADMIT"