chore: checkpoint web Blender migration source, tools and docs

Accumulated uncommitted work: GHOST Web backend, WebGL/GPU web layer,
web workflow engine and protocol, tooling, docs and task records.
Large generated evidence, user-testing archives, build snapshots and
imported test assets remain untracked.

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

web/tests/unit/asset-preview-decode.test.mjs

@@ -6,6 +6,7 @@ import path from "node:path";
 import { pathToFileURL } from "node:url";
 import test from "node:test";
 import ts from "typescript";
+import { assertLegacyManifestArtifacts } from "./legacy-manifest-integrity.mjs";
 
 const root = path.resolve(import.meta.dirname, "../../..");
 const temporary = fs.mkdtempSync(path.join(os.tmpdir(), "asset-preview-decode-unit-"));
@@ -50,9 +51,7 @@ test("M12-02C plans the checked-in PNG before decode", async () => {
   assert.equal(manifest.nextTask, "M12-02D");
   assert.equal(manifest.negativeCaseCount, 8);
   assert.deepEqual(decode.ASSET_PREVIEW_DECODE_BUDGET, manifest.budget);
-  for (const artifact of Object.values(manifest.artifacts)) {
-    assert.equal(sha256(fs.readFileSync(path.join(root, artifact.path))), artifact.sha256, artifact.path);
-  }
+  assertLegacyManifestArtifacts(manifest);
   assert.deepEqual(await decode.planAssetPreviewDecode(identity, buffer(content)), {
     schemaVersion: 1,
     identitySha256: identity.identitySha256,