[codex] reduce lint noise (#3931)

* chore: reduce lint noise

* fix: address lint cleanup review notes

* fix(test): restore url param in mcp-proxy fetch overrides

The lint cleanup renamed (url, opts) to (_url, opts) in two
globalThis.fetch overrides, but the body still references `url`
when forwarding to makeMcpFetch(...)(url, opts). The closure
variable `url` declared in the prior `it()` block does not
survive into these scopes, so the parameter rename introduced
a ReferenceError at runtime.

Revert the rename for the two sites that actually use the
parameter; the third SSE-handler override at line 544 stays
`_url` (genuinely unused).

Addresses greptile P1 on PR #3931.