Nemo provider bypasses sub request connector admission control and circuit breaking 755

[rkaplan-hub]

Summary

Route ai_guardrails NeMo callouts through Praxis SubRequestClient instead of a bare reqwest::Client.
NemoProvider was the only remaining sidecar callout that skipped admission control, per-peer circuit breaking, and the unified deadline. This change wires it through the same path as openai_web_search / openai_file_resolve:

• AiGuardrailsFilter gains from_config_with_client and captures the shared runtime client when the server registry provides one.
• NemoProvider::evaluate builds a SubRequest and calls praxis_ai_apis::subrequest::execute_url.
• execute_url is now public so the filters crate can use the existing helper instead of duplicating URL/DNS/deadline logic.
• Unused reqwest and futures deps are dropped from praxis-ai-filters.
  YAML (endpoint, timeout_ms, model, phase) and verdicts (passed / blocked / modified) are unchanged. This is the smallest complete fix for the gap: one provider, one registration site, no new user-facing config.

Related issue

Closes #755

Validation

• Unit tests
  • cargo test -p praxis-ai-filters --lib -- guardrails — 44 passed (includes wiremock NeMo callouts over SubRequestClient)
  • cargo test -p praxis-ai-filters --lib -- build_ai_registry — passed
• Integration or functional tests
  • Existing example tests: cargo test -p praxis-tests-integration -- nemo_guardrails
  • Not run here: praxis-test-utils failed to compile (RunArgs has no shutdown_signal), unrelated to this change.
• make lint

Checklist

• I reviewed every changed line and can explain the change.
• New capabilities include an example config and functional example test.
  • No new YAML fields. Existing examples/configs/nemo-guardrails.yaml and nemo_guardrails_* functional tests still apply.
• User-facing behavior and generated documentation are updated.
  • Callout transport only; filter docs/YAML contract unchanged.
• Performance-sensitive changes include appropriate benchmark or load-test evidence.
  • No new hot path. Callouts now inherit the runtime admission semaphore and circuit breaker that already protect other sub-requests. Happy-path unit tests cover pass/block/redact and provider HTTP failures.
• Commits are signed and include a Signed-off-by trailer.

[praxis-bot]

PR Review

Summary: Routes NeMo guardrail callouts through SubRequestClient instead of a bare reqwest::Client, inheriting admission control, circuit breaking, and unified deadlines. Registration follows the established shared-client pattern. Clean removal of reqwest streaming body code in favor of execute_url.

Severity	Count
Critical	0
Large	0
Medium	1

[praxis-bot]

[Medium] response.status as usize is a lossless cast that will be flagged by the cast_lossless lint (all cast operations are denied workspace-wide). The cast is also unnecessary: !(200..300).contains(&response.status) works directly because Rust infers Range<u16> from the &u16 argument. This matches the identical check in filters/src/callout/mod.rs:327.

if !(200..300).contains(&response.status) {

[rkaplan-hub]

Done