OTLP header parsing breaks when value contains = (e.g. Sentry's) #22202

Description

oltp.ts splits OTEL_EXPORTER_OTLP_HEADERS on every = instead of just the first.
Headers like Sentry's x-sentry-auth=sentry sentry_key=KEY silently lose the
key portion, causing 401s with no error logged.

Plugins

none

OpenCode version

1.4.3

Steps to reproduce

1. Set OTLP env vars where the header value contains =:
   OTEL_EXPORTER_OTLP_ENDPOINT="https://example.com/otlp"
   OTEL_EXPORTER_OTLP_HEADERS="x-sentry-auth=sentry sentry_key=abc123"

2. Run opencode serve --print-logs

3. Observe: no traces arrive at the backend. No error is logged.

Screenshot and/or share link

None

Operating System

Macos

Terminal

None