test(energy_wiring): opt out of #294 default-agent fallback in _energy_config

Follow-up on @TX-Huang's PR #294. The default-agent fallback now
routes `jarvis ask "..."` (no --agent) through `config.agent.default_agent`,
which dataclass-defaults to `"simple"`. The autouse `_clean_registries`
fixture in tests/conftest.py clears AgentRegistry between tests, so
the fallback then fails with `Unknown agent: simple` and every
CLI-driven test_energy_wiring test exits with code 1.

These tests exercise engine-level instrumentation, not agent dispatch
— ``test_engine_wrapped_with_instrumented``, the energy-monitor
lifecycle tests, and the end-to-end pipeline tests all care that the
engine gets wrapped and telemetry lands in SQLite, regardless of
whether the call goes through an agent. Set ``cfg.agent.default_agent
= ""`` in ``_energy_config`` to keep these tests on the direct-engine
path they were originally designed for. The dedicated
``test_agent_mode_uses_instrumented_engine`` (which explicitly passes
``--agent``) is unaffected.

Same pattern PR #294 already uses in tests/cli/test_ask_router.py
for the two MagicMock-config tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/telemetry/test_energy_wiring.py

@@ -88,6 +88,11 @@ def _energy_config(tmp_path, gpu_metrics=True):
     cfg.telemetry.gpu_metrics = gpu_metrics
     cfg.telemetry.energy_vendor = ""
     cfg.telemetry.db_path = str(tmp_path / "telemetry.db")
+    # These tests exercise engine-level instrumentation, not agent dispatch.
+    # `jarvis ask` (no --agent) now falls back to ``agent.default_agent``
+    # which defaults to "simple", and conftest clears the registry per test.
+    # Opt out explicitly so the CLI uses direct-engine mode here.
+    cfg.agent.default_agent = ""
     return cfg