fix(api): install import-in-the-middle hook for ESM auto-instrumentation

[alextnetto]

What's broken

After deploying #5, metrics and logs flowed to Grafana fine, but Tempo received zero spans:

• otelcol_receiver_accepted_spans_total was empty
• The x-trace-id response header was absent on every API response
• Pino log records had service_name=pagent-api but no trace_id/span_id correlation

Root cause

@opentelemetry/auto-instrumentations-node patches modules at import time. With Node 22 + ESM + --experimental-strip-types, --import ./tracing.ts evaluates our SDK config before server.ts, but the import-in-the-middle loader hook has to be installed via Node's module hook registry — registering it from inside an already-loaded module is too late for built-ins like node:http. So getNodeAutoInstrumentations loaded but silently never wrapped anything.

The OTel team's standard solution is node --import @opentelemetry/auto-instrumentations-node/register, but that bootstraps its own NodeSDK (configured via env vars), which would conflict with our custom-configured SDK in tracing.ts (we wire metric reader + log processor + pino correlation).

Fix

A four-line apps/api/instrument.mjs that registers the loader hook only — leaves SDK setup to tracing.ts:

import { register } from 'node:module';
register('import-in-the-middle/hook.mjs', import.meta.url);

Wired in via a second --import flag (instrument.mjs runs before tracing.ts):

node --experimental-strip-types --import ./instrument.mjs --import ./tracing.ts server.ts

Verification

• npm test (162 tests pass)
• npm run typecheck (clean)
• After merge + Railway redeploy: confirm otelcol_receiver_accepted_spans_total > 0 in Grafana, and x-trace-id header is present on curl -i https://pagent.up.railway.app/health.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
pagent	Ready	Preview, Comment	May 11, 2026 0:35am

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Declare import-in-the-middle as a direct dependency

instrument.mjs now imports import-in-the-middle/hook.mjs, but apps/api/package.json does not declare import-in-the-middle directly. This currently works only when the package manager hoists that transitive dependency; in non-hoisted or isolated installs (common in CI/deploy/container builds), startup will fail with ERR_MODULE_NOT_FOUND before the API boots. Please add import-in-the-middle to dependencies so the new boot path is deterministic across install environments.

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