fix(api/mcp): unbreak Railway deploy — strip-types incompat in rate-limit.ts

[alextnetto]

Summary

Production has been serving stale code since 2026-05-09 17:51 PT because every Railway deploy attempt has failed with:

SyntaxError [ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX]: TypeScript parameter property is not supported in strip-only mode
file:///app/apps/api/mcp/rate-limit.ts:39
  constructor(
    private readonly limit: number,
                     ^^^^^^^^^^^^^

npm run start boots via node --experimental-strip-types, which strips type annotations but cannot emit the field assignments that parameter properties imply. The class fails to load, the process exits 1, the healthcheck never goes green on the new container, so Railway keeps the previous (working) container in front of traffic. Result: ~18 failed deploys over 18 hours, all silent because the old version kept answering /health 200.

Fix

Promote limit and windowMs to explicit fields and assign them in the constructor body. No behavior change; same shape on disk.

Verified locally

• node --experimental-strip-types loads rate-limit.ts cleanly (OK: [ 'RateLimiter' ])
• Booting the API end-to-end gets past TS loading and reaches DB connect (only fails locally because no Postgres on :5432)
• Pre-push: typecheck + lint + format + 158 tests + mcp bundle — all green

Test plan

• CI green
• Watch Railway deploy after merge — should turn the new container green for the first time since 2026-05-09
• curl https://pagent.up.railway.app/health returns {"ok":true,"db":"ok"} (the new shape)