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* ci: cancel superseded eval runs; relax LLM-judge clarity bar to 3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/test-free.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# bun run test:ubicloud [test:free args] — run the free suite on an ephemeral
+# Ubicloud VM (standard-16 unless UBI_SIZE says otherwise) with the required CI
+# lane's environment. Shard logs land in .context/ubicloud/<timestamp>/.
+# With --record-durations, the refreshed scripts/free-test-durations.json is
+# copied back into this checkout.
+set -euo pipefail
+
+here=$(cd "$(dirname "$0")" && pwd)
+root=$(cd "$here/../.." && pwd)
+logs="$root/.context/ubicloud/$(date +%Y%m%d-%H%M%S)"
+
+args=(--src "$root" --setup "$here/setup-free-suite.sh"
+  --env GSTACK_EXPECT_BINARIES=1 --env GSTACK_FREE_RETRY_FLAKY=1
+  --pull "/tmp/gstack-free-test-*:$logs")
+[ -z "${GSTACK_FREE_JOBS:-}" ] || args+=(--env "GSTACK_FREE_JOBS=$GSTACK_FREE_JOBS")
+for arg in "$@"; do
+  [ "$arg" != --record-durations ] || args+=(--pull "work/$(basename "$root")/scripts/free-test-durations.json:$root/scripts")
+done
+
+"$here/ubi-runner.sh" run "${args[@]}" -- "xvfb-run -a bun run test:free $*"