facet-id-ioctx repro fixture

Endpoints:
  GET /partyserver/<facetName>
    - partyserver `Server.name` getter path. Reads
      `this.ctx.id.name` via the getter at
      `packages/partyserver/src/index.ts:776`.
  GET /raw/<facetName>
    - bypass partyserver, read `this.ctx.id.name` directly.

  GET /faulted/<facetName>
    - fault-injection: stub `ctx.id` with a Proxy that
      throws the production cross-IoContext error, then
      call partyserver's `name` getter. Pre-fix throws;
      post-fix should fall back to the `__ps_name`
      storage record and return `<facetName>`.

Empirical baseline:
  - vite dev:                /partyserver, /raw -> 200
                             /faulted          -> 500
  - wrangler dev:            same as vite dev
  - wrangler dev --remote:   same as vite dev (production
                             preview workerd does NOT
                             reproduce the bug either)
  - wrangler deploy:         /partyserver, /raw -> 500
                             with the IoContext error
                             (per cloudflare/agents#1410
                             reporter; awaiting confirmation)