fix: resolve 18 QA-discovered bugs across tools, previews, and the AI pipeline (#242)

Exhaustive QA sweep of all 157 tools. Fixes: CSP blob media, csv-excel ExcelJS interop, ocr-pdf segfault, chart-maker upload, non-PDF doc preview, RAW decode, merge-tool multi-file path, html-to-image chromium, ogv/wma/amr/ac3 preview fallbacks, meme/gif/stabilize codecs, nav+home a11y. Plus orphan-format and test-debt cleanup, the AI bundle build script, and a reusable Playwright QA harness under tests/qa/.

tests/qa/generate-ledger.mts

@@ -0,0 +1,60 @@
+// Generates the master coverage ledger (157 rows, complete by construction) from
+// tools-meta.json. Discovery shards update cells; any "pending" cell at the end is
+// an explicit, surfaced gap. Run: npx tsx tests/qa/generate-ledger.mts
+import { readFileSync, writeFileSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+interface ToolMeta {
+  id: string;
+  name: string;
+  modality: string;
+  acceptedInputs: string[];
+  executionHint: string;
+  isAI: boolean;
+}
+
+const dir = path.dirname(fileURLToPath(import.meta.url));
+const meta: ToolMeta[] = JSON.parse(readFileSync(path.join(dir, "tools-meta.json"), "utf8"));
+
+// Cells: "pending" | "pass" | "fail" | "n/a"; counts are integers.
+const tools = meta.map((t) => ({
+  toolId: t.id,
+  name: t.name,
+  modality: t.modality,
+  executionHint: t.executionHint,
+  isAI: t.isAI,
+  acceptedFormats: t.acceptedInputs,
+  acceptedFormatCount: t.acceptedInputs.length,
+  inputFormatsTested: 0,
+  inputFormatsTotal: t.acceptedInputs.length,
+  settingsTested: "pending",
+  outputFormatsTested: "pending",
+  multiFile: "pending",
+  inputPreview: "pending",
+  outputPreview: "pending",
+  download: "pending",
+  negativePath: "pending",
+  consoleClean: "pending",
+  status: "pending",
+  bugs: [] as string[],
+}));
+
+const out = path.join(dir, "..", "..", "docs", "qa", "coverage-ledger.json");
+writeFileSync(
+  out,
+  `${JSON.stringify(
+    {
+      generatedAtNote: "stamp set by harness at run time",
+      toolCount: tools.length,
+      byModality: tools.reduce<Record<string, number>>((acc, t) => {
+        acc[t.modality] = (acc[t.modality] ?? 0) + 1;
+        return acc;
+      }, {}),
+      tools,
+    },
+    null,
+    2,
+  )}\n`,
+);
+console.log(`ledger: ${tools.length} tools -> ${out}`);