ci: build tfjs-node native addon for firestore-semantic-search and storage-reverse-image-search

[cabljac]

Problem

The Testing workflow is red on every PR (e.g. observed on #1059). firestore-semantic-search:test fails to even load 5 suites:

The Node.js native addon module (tfjs_binding.node) can not be found at path:
  .../@tensorflow/tfjs-node/lib/napi-v8/tfjs_binding.node
> 17 | require('@tensorflow/tfjs-node');

Root cause

.github/workflows/test.yaml installs dependencies with npm ci --ignore-scripts and lerna bootstrap --ignore-scripts. --ignore-scripts skips the @tensorflow/tfjs-node postinstall, which is what fetches/builds its native addon (tfjs_binding.node) and libtensorflow. Every firestore-semantic-search suite that require('@tensorflow/tfjs-node') then throws at module load, failing lerna run test and the whole workflow. (Earlier green runs were riding a warm node_modules cache that still held the addon.)

This is unrelated to the historically xtest-disabled flaky tests in that extension and unrelated to the genai-chatbot flake fix.

Fix

Add a retried CI step after bootstrap that rebuilds the addon from source for firestore-semantic-search/functions:

npm rebuild @tensorflow/tfjs-node --build-addon-from-source

Building from source (rather than relying on prebuilt binaries that may not cover the CI Node version) is the robust option and is retried 3× to tolerate transient libtensorflow download failures.

[IzaakGough]

Lgtm