[codex] Limit foreground API timeout

[jverre]

Summary

• Reduce foreground hook Opik API timeout from 30s to 2s so Claude Code does not wait tens of seconds when Opik is unreachable.
• Add an explicit API constructor for longer background calls and keep the detached /context worker on the 30s timeout.
• Cover the timeout split with a small unit test.

Validation

• go test ./...
• go vet ./...
• git diff --check