v1.91.5.0 feat: balanced free-suite shards, test:ubicloud, and faster PR eval lane (#2989)

* v1.91.5.0 feat: balanced free-suite shards, 16-way Linux runs, and bun run test:ubicloud

* chore: regenerate agents digest for v1.91.5.0

* ci: serial flaky retry and flake ledger for the Windows free lane

* ci: cancel superseded eval runs; relax LLM-judge clarity bar to 3

scripts/ubicloud/setup-free-suite.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+# Bootstrap a fresh ubuntu-noble Ubicloud VM to run the free suite exactly as
+# the required CI lane does (.github/workflows/free-tests.yml, free-suite job).
+# Runs as user `ubi` (passwordless sudo) from the synced checkout.
+set -euo pipefail
+
+BUN_VERSION=1.4.0
+NODE_VERSION=22.20.0
+
+export DEBIAN_FRONTEND=noninteractive
+sudo -E apt-get update -qq
+sudo -E apt-get install -y -qq --no-install-recommends \
+  git curl unzip xz-utils ca-certificates build-essential clang python3-venv jq \
+  xvfb x11-utils poppler-utils fonts-noto-color-emoji >/dev/null
+
+# Ubuntu 24.04 blocks unprivileged user namespaces, which Chromium's sandbox
+# needs; GitHub-hosted runners ship with this relaxed.
+sudo sysctl -qw kernel.apparmor_restrict_unprivileged_userns=0
+
+if ! command -v node >/dev/null; then
+  curl -fsSL "https://nodejs.org/dist/v$NODE_VERSION/node-v$NODE_VERSION-linux-x64.tar.xz" \
+    | sudo tar -xJ -C /usr/local --strip-components=1
+fi
+
+if [ ! -x "$HOME/.bun/bin/bun" ]; then
+  curl -fsSL https://bun.sh/install | bash -s "bun-v$BUN_VERSION" >/dev/null
+fi
+grep -q '.bun/bin' "$HOME/.profile" || echo 'export PATH="$HOME/.bun/bin:$PATH"' >>"$HOME/.profile"
+export PATH="$HOME/.bun/bin:$PATH"
+
+git config --global user.email "free-tests@gstack.test"
+git config --global user.name "Free Tests"
+git config --global init.defaultBranch main
+git config --global --add safe.directory '*'
+
+bun install --frozen-lockfile
+bunx playwright install --with-deps chromium
+
+chrome=$(bun -e 'import { chromium } from "playwright"; import { realpathSync } from "node:fs"; console.log(realpathSync(chromium.executablePath()))')
+sudo install -T -o root -g root -m 4755 "${chrome%/*}/chrome_sandbox" "${chrome%/*}/chrome-sandbox"
+
+{
+  bun run gen:skill-docs --host all
+  bun run vendor:xterm
+  bash browse/scripts/build-node-server.sh
+  bun run build:gates
+  bun run build:cso
+} >/dev/null