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/e2e/b3-pack-path-probe.spec.ts

@@ -0,0 +1,49 @@
+import fs from "node:fs";
+import path from "node:path";
+import { test } from "@playwright/test";
+import { NativeUIWorkflow, observeNative } from "../fixtures/native-ui-workflow";
+
+const root = path.resolve(import.meta.dirname, "../../..");
+const fixture = path.join(root, "blender-5.2.0/tests/files/sequence_editing/effects/fx_comp.blend");
+
+test("probe filepath and external image resolution in browser session", async ({ page }, testInfo) => {
+  test.setTimeout(180_000);
+  await observeNative(page);
+  await page.goto("/");
+  const flow = new NativeUIWorkflow(page, testInfo.outputPath("cases"));
+  await flow.command(() => page.getByTestId("blend-file-input").setInputFiles(fixture));
+  const out = await page.evaluate(async () => {
+    const worker = (window as any).__nativeWorkflowEngine as Worker;
+    const send = (command: any) => new Promise<any>((resolve, reject) => {
+      const requestId = `path-${crypto.randomUUID()}`;
+      const receive = (event: MessageEvent) => {
+        if (event.data?.requestId !== requestId || event.data?.kind !== 'result') return;
+        worker.removeEventListener('message', receive);
+        if (event.data.ok) resolve(event.data.result); else reject(new Error(`${event.data.error?.code ?? 'NATIVE'}: ${event.data.error?.message ?? JSON.stringify(event.data.error)}`));
+      };
+      worker.addEventListener('message', receive); worker.postMessage({ requestId, command });
+    });
+    const source = [
+      "import bpy, os, json",
+      "print('FILEPATH', repr(bpy.data.filepath))",
+      "print('ABS_MASK', bpy.path.abspath('//mask.png'))",
+      "print('IMAGES', json.dumps([{'n': i.name, 'fp': i.filepath, 'packed': i.packed_file is not None} for i in bpy.data.images]))",
+      "print('EXISTS', os.path.exists(bpy.path.abspath('//mask.png')))",
+      "print('ROOTS', json.dumps(sorted(os.listdir('/'))))",
+      "try:",
+      "    print('PACK', bpy.ops.file.pack_all())",
+      "except Exception as e:",
+      "    print('PACK_ERROR', type(e).__name__, str(e)[:200])",
+      "print('IMAGES_AFTER', json.dumps([{'n': i.name, 'packed': i.packed_file is not None} for i in bpy.data.images]))",
+    ].join("\n");
+    const log: any = {};
+    try {
+      const r = await send({ type: 'jsonCommand', cmd: 'pythonExec', params: { source, filename: 'PathProbe.py', console: false } });
+      log.state = r.json?.state;
+      log.output = String(r.json?.output ?? '').slice(0, 2000);
+      log.revisionBeforeAfter = r.snapshot?.revision;
+    } catch (e: any) { log.error = String(e?.message ?? e); }
+    return log;
+  });
+  fs.writeFileSync("/tmp/pack-path-probe.json", JSON.stringify(out, null, 2));
+});