test(make-pdf): fill ship-audit coverage gaps — downscale, reset contract, excalidraw fence, WebP

Ship coverage audit found 9 gaps (85%); this fills the 2 HIGH + 3 MEDIUM and
most LOW. diagram-gate fixture gains a 4200px incompressible photo (the only
live coverage of __downscaleRaster AND the 64KB chunked jsViaBuffer eval
transport — asserted via the downscale stderr warning), an ```excalidraw
scene fence rendered through exportToSvg (vector labels + caption in
pdftotext, no leaked scene JSON), and the broken fence MOVED BETWEEN the two
mermaid fences so the second diagram rendering proves the D6.2 reset
contract end-to-end. New coverage-gaps.test.ts (16 tests): mock-tab reset
contract (exactly one reload, post-failure fence renders), excalidraw
fail-fast diagnostic without a bundle call, rasterize error fallbacks
(figure/tag kept, never silent), WebP VP8/VP8L/VP8X byte parsers,
landscapeContentBox a4/asymmetric margins, bare-token slot fallback,
resolveBundlePath env override + error shape, screenCss media scoping.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

make-pdf/test/e2e/diagram-gate.test.ts

@@ -78,25 +78,43 @@ describe("diagram render gate", () => {
     const outputPdf = path.join(workDir, "out.pdf");
     const ppmPrefix = path.join(workDir, "page");
     try {
-      execFileSync(PDF_BIN, ["generate", FIXTURE, outputPdf, "--quiet"], {
-        encoding: "utf8",
+      // No --quiet: stderr carries the downscale warning asserted below.
+      const run = Bun.spawnSync([PDF_BIN, "generate", FIXTURE, outputPdf], {
         env: { ...process.env, BROWSE_BIN },
-        stdio: ["ignore", "pipe", "pipe"],
-        timeout: CHILD_TIMEOUT_MS,
+        stdout: "pipe",
+        stderr: "pipe",
       });
+      const stderr = new TextDecoder().decode(run.stderr);
+      if (run.exitCode !== 0) {
+        throw new Error(`generate failed (exit ${run.exitCode}):\n${stderr}`);
+      }
       expect(fs.existsSync(outputPdf)).toBe(true);
 
+      // 0. Print-resolution downscale fired on the 4200px noise photo — this
+      //    is the only live coverage of __downscaleRaster AND the chunked
+      //    jsViaBuffer transport (the data URI exceeds the 100KB argv path).
+      expect(stderr).toMatch(/downscaled huge-noise\.png 4200px → \d+px/);
+
       const pdftotext = resolvePopplerTool("pdftotext")!;
       const text = execFileSync(pdftotext, [outputPdf, "-"], { encoding: "utf8", timeout: CHILD_TIMEOUT_MS });
 
-      // 1. Vector text from BOTH diagrams (multi-fence + id-collision check —
-      //    a collided render drops the second diagram's content).
+      // 1. Vector text from BOTH diagrams (multi-fence + id-collision check).
+      //    The broken fence sits BETWEEN them in the fixture, so the second
+      //    diagram rendering at all proves the reset contract (D6.2): the
+      //    bundle page reloaded after the failure and kept working.
       for (const label of ["gatealphanode", "gatebetanode", "gategammanode", "gatedeltanode", "gateepsilonnode"]) {
         expect(text).toContain(label);
       }
 
-      // 2. Rendered fences must NOT ship raw mermaid; render=false must.
+      // 1b. The excalidraw fence rendered through exportToSvg (vector text
+      //     from the scene file, plus its caption).
+      expect(text).toContain("excalialphanode");
+      expect(text).toContain("excalibetanode");
+      expect(text).toContain("Converted flowchart");
+
+      // 2. Rendered fences must NOT ship raw mermaid/scene JSON; render=false must.
       expect(text).not.toContain("GATEALPHA[");
+      expect(text).not.toContain('"type":"excalidraw"');
       expect(text).toContain("RAWKEPT");
       expect(text).toContain("ASCODE");