fix(openclaw): make verify fail on unhealthy backend

[MatrixAdventurer]

Summary

• make openclaw memoria verify run a real openclaw memoria health check before reporting success
• fail verification when the configured backend is unreachable, even if plugin/config wiring looks valid
• include backend-specific hints in the verification output and document the stricter verify behavior in the README

Why

I hit a local false-positive case where verify returned ok: true even though the configured Memoria backend was not healthy and normal memory operations were already failing at runtime.

That made verify good at checking install wiring, but not good enough at answering the practical question users care about: "is this setup actually usable right now?"

This change makes verify a better post-install / post-setup diagnostic by requiring a successful health check before it reports success.

What changed

• add a non-throwing command runner in verify_plugin_install.mjs
• run openclaw memoria health --user-id ... as part of verification
• return a non-zero exit when health fails
• keep backend-specific hints in the output:
  • embedded: check MatrixOne reachability
  • embedded + embeddingProvider=local: remind users that the binary must be built with local-embedding
  • http: check remote API reachability
• keep deeper follow-up checks after health succeeds
• update README verification notes

Local testing

Passed locally:

• node --check plugins/openclaw/scripts/connect_openclaw_memoria.mjs
• node --check plugins/openclaw/scripts/verify_plugin_install.mjs
• connector smoke test with a temp config path (connect_openclaw_memoria.mjs writes the expected cloud config)
• reproduced the original false-positive scenario and confirmed verify_plugin_install.mjs now exits non-zero with health details and hints instead of returning ok: true

[MatrixAdventurer]

For broader project context, this work lives in the Memoria repo itself:
https://github.com/matrixorigin/Memoria

[MatrixAdventurer]

Quick maintenance note: the implementation/result still looks useful, but this branch is now dirty against current main. A rebase should be enough to make it reviewable again.