feat: completude de l'editeur Excel - mise en forme, sortie, concurrence, cache, outils IA #156

L'editeur lisait les styles mais ne les ecrivait pas, exportait la feuille
entiere et laissait le dernier-ecrivain gagner entre processus.

- A8 : bouton Mise en forme (gras/italique/souligne, alignements, couleurs via
  selecteur natif, formats de nombre, fusion, volets figes, largeur/hauteur) et
  nouvelle route PUT .../xlsx/style (verrou, backup, swap atomique, garde de
  perte, If-Match) ; A9 : decision "pas de moteur de formule" annoncee dans
  l'UI ; A10 : undo/redo unifie, piles par fichier conservees au re-rendu
- A11 : export de la selection + Markdown/HTML/impression et recherche sur
  toutes les feuilles ; A12 : concurrence optimiste (If-Match -> 409 reparable,
  retry qui relit) ; A13 : cache des metadonnees par (chemin, mtime, taille)
- A14 : outils IA .xlsm/.csv + search_workbook, analyze_range,
  edit_xlsx_structure
- tests : test_xlsx_styles.py (17), test_spreadsheet_tools.py (34),
  TestOptimisticConcurrency/TestMetaCache, JSDOM xlsx-viewer 107/107

tests/test_xlsx_styles.py

@@ -35,6 +35,20 @@ def styled_book(test_vault_dir: str) -> str:
     return str(path)
 
 
+@pytest.fixture
+def plain_book(test_vault_dir: str) -> str:
+    """An unstyled workbook — the write side starts from a blank slate."""
+    path = Path(test_vault_dir) / "plain.xlsx"
+    wb = openpyxl.Workbook()
+    ws = wb.active
+    ws.title = "Data"
+    ws.append(["Nom", "Valeur"])
+    ws.append(["a", 1])
+    ws.append(["b", 2])
+    wb.save(path)
+    return str(path)
+
+
 class TestStyleReading:
     def test_bold_italic_and_font_color(self, styled_book):
         from backend.xlsx_reader import read_sheet_styles
@@ -82,6 +96,160 @@ class TestStyleReading:
         assert read_sheet_styles(bad, "Data") == {}
 
 
+class TestStyleWriting:
+    """#156-A8 — the viewer can now WRITE formatting, not just read it.
+
+    One locked, atomic rewrite through ``PUT …/xlsx/style``: styles (bold,
+    italic, underline, colours, alignment, number format), merges, column
+    widths, row heights and frozen panes.
+    """
+
+    def _style(self, client, path, ops, **extra):
+        return client.put(
+            f"/api/file/{VAULT}/xlsx/style",
+            params={"path": path},
+            json={"ops": ops, **extra},
+        )
+
+    def test_styles_survive_a_reload(self, client, plain_book):
+        resp = self._style(client, "plain.xlsx", [
+            {
+                "op": "cell", "sheet": "Data", "range": "A1:B1",
+                "style": {
+                    "bold": True, "italic": True, "underline": True,
+                    "font_color": "#cc0000", "fill_color": "#ffe08a",
+                    "align": "center", "number_format": "0.00",
+                },
+            },
+        ])
+        assert resp.status_code == 200
+        assert resp.json()["revision"]
+        wb = openpyxl.load_workbook(plain_book)
+        ws = wb["Data"]
+        assert ws["A1"].font.bold is True and ws["A1"].font.italic is True
+        assert ws["A1"].font.underline == "single"
+        assert ws["A1"].font.color.rgb == "FFCC0000"
+        assert ws["A1"].fill.start_color.rgb == "FFFFE08A"
+        assert ws["A1"].alignment.horizontal == "center"
+        assert ws["B1"].number_format == "0.00"
+        assert ws["A1"].value == "Nom", "the value is untouched"
+        assert not ws["A2"].font.bold, "a neighbour outside the range is untouched"
+        wb.close()
+
+    def test_the_written_style_is_read_back_by_the_viewer(self, client, plain_book):
+        self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"bold": True, "fill_color": "#ffe08a"}},
+        ])
+        resp = client.get(f"/api/file/{VAULT}", params={"path": "plain.xlsx"})
+        assert resp.status_code == 200
+        sheet = resp.json()["xlsx_sheets"][0]
+        style = sheet["styles"]["A1"]
+        assert "font-weight:600" in style and "background:#ffe08a" in style
+
+    def test_merges_sizes_and_freeze(self, client, plain_book):
+        resp = self._style(client, "plain.xlsx", [
+            {"op": "merge", "sheet": "Data", "range": "A1:B1"},
+            {"op": "col_width", "sheet": "Data", "col": "A", "width": 24},
+            {"op": "row_height", "sheet": "Data", "row": 2, "height": 30},
+            {"op": "freeze", "sheet": "Data", "cell": "A2"},
+        ])
+        assert resp.status_code == 200
+        wb = openpyxl.load_workbook(plain_book)
+        ws = wb["Data"]
+        assert [str(r) for r in ws.merged_cells.ranges] == ["A1:B1"]
+        assert ws.column_dimensions["A"].width == 24
+        assert ws.row_dimensions[2].height == 30
+        assert str(ws.freeze_panes) == "A2"
+        wb.close()
+
+        resp = self._style(client, "plain.xlsx", [
+            {"op": "unmerge", "sheet": "Data", "range": "A1:B1"},
+            {"op": "freeze", "sheet": "Data", "cell": ""},
+        ])
+        assert resp.status_code == 200
+        wb = openpyxl.load_workbook(plain_book)
+        ws = wb["Data"]
+        assert not list(ws.merged_cells.ranges)
+        assert ws.freeze_panes is None
+        wb.close()
+
+    def test_a_style_can_be_cleared(self, client, plain_book):
+        self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"bold": True, "font_color": "#cc0000", "fill_color": "#ffe08a"}},
+        ])
+        resp = self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"bold": False, "font_color": "", "fill_color": "", "number_format": "General"}},
+        ])
+        assert resp.status_code == 200
+        wb = openpyxl.load_workbook(plain_book)
+        ws = wb["Data"]
+        assert ws["A1"].font.bold in (None, False)
+        assert ws["A1"].font.color is None
+        assert ws["A1"].fill.fill_type is None
+        assert ws["A1"].number_format == "General"
+        wb.close()
+
+    def test_invalid_inputs_are_refused(self, client, plain_book):
+        bad_style = self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"blink": True}},
+        ])
+        assert bad_style.status_code == 400
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {}},
+        ]).status_code == 400
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"fill_color": "rouge"}},
+        ]).status_code == 400
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "pas-une-plage", "style": {"bold": True}},
+        ]).status_code == 400
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Nope", "range": "A1", "style": {"bold": True}},
+        ]).status_code == 400
+        assert self._style(client, "plain.xlsx", [{"op": "spin", "sheet": "Data"}]).status_code == 400
+        assert self._style(client, "plain.xlsx", []).status_code == 400
+        assert self._style(client, "plain.xlsx", [
+            {"op": "col_width", "sheet": "Data", "col": "A", "width": 900},
+        ]).status_code == 400
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"align": "diagonal"}},
+        ]).status_code == 400
+
+    def test_a_csv_is_refused(self, client, test_vault_dir):
+        (Path(test_vault_dir) / "style.csv").write_text("a,b\n1,2\n", encoding="utf-8")
+        resp = self._style(client, "style.csv", [
+            {"op": "cell", "sheet": "x", "range": "A1", "style": {"bold": True}},
+        ])
+        assert resp.status_code == 400
+
+    def test_a_stale_revision_is_refused_and_the_fresh_one_accepted(self, client, plain_book):
+        first = self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"bold": True}},
+        ])
+        assert first.status_code == 200
+        stale = self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A2", "style": {"bold": True}},
+        ], if_match="deadbeef-1")
+        assert stale.status_code == 409
+        assert stale.json()["details"]["reason"] == "stale_revision"
+        fresh = self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A2", "style": {"bold": True}},
+        ], if_match=first.json()["revision"])
+        assert fresh.status_code == 200
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A3", "style": {"bold": True}},
+        ], if_match=42).status_code == 400
+
+    def test_a_backup_is_written_before_the_rewrite(self, client, plain_book):
+        from backend.services.backups import get_backup_dir
+
+        assert self._style(client, "plain.xlsx", [
+            {"op": "cell", "sheet": "Data", "range": "A1", "style": {"bold": True}},
+        ]).status_code == 200
+        backups = list(get_backup_dir(VAULT, "plain.xlsx").glob("plain.xlsx.*.bak"))
+        assert backups, "the rewrite is backed up first"
+
+
 class TestEndpointWiring:
     def test_read_response_carries_styles_merges_freeze(self, client, styled_book):
         resp = client.get(f"/api/file/{VAULT}", params={"path": "styles.xlsx"})