refactor(telemetry): collapse 6 OpenTelemetry no-op stubs into one proxy

[Kamilbenkirane]

What

When opentelemetry-api is not installed, telemetry.py falls back to six hand-written no-op stand-ins — _NoOpSpan, _NoOpTracer, _NoOpStatus, _NoOpStatusCode, _NoOpHistogram, _NoOpMeter. They're near-identical discard-everything boilerplate.

This replaces all six with a single _NoOp proxy that returns itself for every attribute access and call:

class _NoOp:
    ERROR = "ERROR"  # satisfies StatusCode.ERROR
    def __init__(self, *a, **k): ...
    def __call__(self, *a, **k): return self
    def __getattr__(self, name): return self
    def __enter__(self): return self
    def __exit__(self, *a): return None

Net −36 lines (telemetry.py: +24 / −60).

Why it's safe

Every call site the telemetry module makes against these objects is covered by the proxy, and all of them discard return values:

• with tracer.start_as_current_span(...) as span: → __getattr__ → __call__ → __enter__ all return self; span.set_attribute / set_attributes / add_event / record_exception / set_status / end(...) resolve through __getattr__/__call__.
• Status(StatusCode.ERROR, str(exc)) → StatusCode.ERROR is the real class attr "ERROR"; Status(...) instantiates _NoOp and discards args.
• meter.create_histogram(...).record(...) chains through the proxy.
• Special methods (__enter__, __call__) are looked up on the type, so __getattr__ never shadows them. No ==/identity checks are made on Status objects.

_noop_use_span is kept as a separate function — it must yield the passed-in span, which a self-returning proxy would not. The real-OpenTelemetry path is untouched. No behavior change.

Tests

Adds tests/unit_tests/test_telemetry_noop.py driving the _NoOp proxy through every call shape the module uses. The import-fallback path previously had no coverage (the suite always runs with opentelemetry installed).

make ci green: 676 passed, coverage 81.76%, ruff + format + mypy + bandit clean.

Context

This is the single surviving cleanup from a repo-wide over-engineering audit. The audit's other candidates — including a "protocol client dedup" — were investigated and deliberately not done: the chatcompletions/openresponses protocols are a template-driven extension point and only ~14% identical, so merging them would fight the design.

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.