test: reorganize fixture files into modality-first layout (phase 6b)

Move all fixture files from flat/mixed dirs (content/, media/, documents/,
formats/, hostile/, root loose) into the modality-first hierarchy:
image/{valid,formats,edge,hostile}, video/{valid,formats,hostile},
audio/{valid,formats,hostile}, document/{valid,formats,edge,hostile},
data/valid/, security/. Update index.ts paths, fixtureDir aliases,
all literal refs in 17 e2e/qa/script files, manifest.json, and the
three generator scripts. 163 files moved, 0 dropped, 100 new tests
from expanded document scan.

tests/integration/tools/data/csv-excel.test.ts

@@ -84,7 +84,7 @@ describe("csv-excel (pure JS, no skipIf)", () => {
   }, 30_000);
 
   it("converts XLSX to CSV containing the fixture content", async () => {
-    // Use the committed tiny.xlsx from tests/fixtures/documents/
+    // Use the committed tiny.xlsx from tests/fixtures/document/formats/
     // (Sheet1 with "SnapOtter" in A1)
     const res = await runTool("tiny.xlsx", XLSX_FIXTURE, { sheet: 1 });
     expect(res.statusCode).toBe(200);