feat: align local-first workspace direction

Document the VSCode-like local-first product shape, demote Convex to a control-plane role, and retire stale architecture drafts.

Add local workspace migration/export references plus smoke coverage for no-Convex managed workspace startup, local markdown title/body/options persistence, asset upload behavior, and Convex fixture export.

Verification: git diff --cached --check; node scripts/check-local-first-convex-guard.js --staged; node scripts/task444-convex-workspace-export-local-fixture-smoke.js; node scripts/task166-local-first-managed-workspace-no-convex-smoke.js; node scripts/task167-local-markdown-title-body-options-no-convex-smoke.js

scripts/task435-local-folder-watch-no-reload-smoke.js

@@ -9,6 +9,9 @@ const BASE_URL = (process.env.MNOTE_WEB_SMOKE_BASE_URL || "http://127.0.0.1:3000
 const UI_TIMEOUT_MS = Number(process.env.MNOTE_SMOKE_UI_TIMEOUT_MS || 30_000);
 const OUTPUT_DIR = path.join(process.cwd(), "tmp", "task435-local-folder-watch-no-reload-smoke");
 const RESULT_PATH = path.join(OUTPUT_DIR, "result.json");
+const CHROMIUM_EXECUTABLE_PATH = process.env.PLAYWRIGHT_CHROMIUM_EXECUTABLE_PATH
+  || ["/usr/bin/google-chrome-stable", "/usr/bin/google-chrome", "/snap/bin/chromium"]
+    .find((candidate) => fs.existsSync(candidate));
 
 function assert(condition, message) {
   if (!condition) {
@@ -32,6 +35,21 @@ function localMdDocumentId(relativePath) {
   return `local-md:${relativePath.replaceAll("/", "~2F")}`;
 }
 
+function writeWorkspaceManifest(root, ownerId) {
+  const metadataDir = path.join(root, ".mnote");
+  fs.mkdirSync(metadataDir, { recursive: true });
+  fs.writeFileSync(
+    path.join(metadataDir, "workspace.json"),
+    `${JSON.stringify({
+      workspaceId: `local-ws:${ownerId}:task435`,
+      ownerId,
+      createdAt: new Date().toISOString(),
+      capabilities: ["local_files", "markdown_edit"],
+    }, null, 2)}\n`,
+    "utf8",
+  );
+}
+
 async function quickLogin(page) {
   await page.goto(`${BASE_URL}/auth`, { waitUntil: "domcontentloaded", timeout: UI_TIMEOUT_MS });
   const quickLoginButton = page.getByRole("button", { name: "测试账号快速登录" });
@@ -100,12 +118,15 @@ async function run() {
   fs.mkdirSync(OUTPUT_DIR, { recursive: true });
   const root = fs.mkdtempSync(path.join(os.tmpdir(), "mnote-local-watch-no-reload-"));
   fs.mkdirSync(path.join(root, "docs"), { recursive: true });
-  fs.mkdirSync(path.join(root, ".mnote"), { recursive: true });
+  writeWorkspaceManifest(root, "user_real");
   fs.writeFileSync(path.join(root, "README.md"), "# Local Root\n", "utf8");
   fs.writeFileSync(path.join(root, "docs", "stable.md"), "# Stable Page\n", "utf8");
   fs.writeFileSync(path.join(root, "docs", "stable-asset.txt"), "stable asset", "utf8");
 
-  const browser = await chromium.launch({ headless: true });
+  const browser = await chromium.launch({
+    headless: true,
+    ...(CHROMIUM_EXECUTABLE_PATH ? { executablePath: CHROMIUM_EXECUTABLE_PATH } : {}),
+  });
   const context = await browser.newContext({
     viewport: { width: 1280, height: 860 },
     extraHTTPHeaders: {