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-reference-gc.test.mjs

@@ -3,6 +3,7 @@ import crypto from "node:crypto";
 import fs from "node:fs";
 import path from "node:path";
 import test from "node:test";
+import { assertLegacyManifestArtifacts } from "./legacy-manifest-integrity.mjs";
 
 const root = path.resolve(import.meta.dirname, "../../..");
 const manifest = JSON.parse(fs.readFileSync(path.join(root, "tests/golden/M12-02G/manifest.json"), "utf8"));
@@ -15,7 +16,5 @@ test("M12-02G binds final-reference and cross-project reclamation evidence", ()
   assert.equal(manifest.nextTask, "M12-02H");
   assert.deepEqual(manifest.sequence, ["REMOVE_FIRST_REFERENCE", "RETAIN_PAYLOAD", "REMOVE_FINAL_REFERENCE", "COLLECT_PAYLOAD"]);
   assert.equal(manifest.otherProjectPayload, "PRESERVED_READY");
-  for (const artifact of Object.values(manifest.artifacts)) {
-    assert.equal(sha256(artifact.path), artifact.sha256, artifact.path);
-  }
+  assertLegacyManifestArtifacts(manifest);
 });