Add: tool-smoke gate inside each DFX scene test

[ChaoWao]

Summary

Each DFX capture pipeline (dep_gen, l2_swimlane, tensor_dump) ships with a consumer script under simpler_setup/tools/. The corresponding scene test now invokes the consumer against the artifact it just produced and asserts exit code 0. A future schema change that breaks a tool fails the same CI step that captured the artifact — no silent tooling rot.

• Smoke is exit-code-only. HTML / PDF / Perfetto JSON content is not validated. The contract is "the tool still parses this schema".
• PMU has no smoke — there's no consumer tool for raw pmu.csv.
• sched_overhead_analysis is intentionally skipped — it needs a real device log and would false-positive on sim. Reserve for a future hardware DFX smoke.

Wiring

Each test calls the consumer via a plain subprocess.run([sys.executable, "-m", "simpler_setup.tools.<name>", artifact, ...], check=True, timeout=60) — stdlib only, no helper module:

• tests/.../dfx/dep_gen/test_dep_gen.py — smokes deps_to_graph in both default and --show-tensor-info modes, guarded by shutil.which("dot") so dev machines without graphviz skip cleanly.
• tests/.../dfx/l2_swimlane/test_l2_swimlane.py — smokes swimlane_converter against l2_perf_records.json.
• tests/.../dfx/tensor_dump/test_tensor_dump.py — smokes dump_viewer against the captured tensor_dump/ directory.
• .github/workflows/ci.yml — installs graphviz on the github-hosted sim runners (Linux apt + macOS brew); the self-hosted onboard a2a3 runner emits a ::warning:: if dot is missing, then the shutil.which guard skips that one smoke without failing CI.

Test plan

• All 4 dfx tests pass via pytest --platform a2a3sim on macOS arm64 with corresponding --enable-* flags
• _smoke_deps.html, _smoke_deps_with_tensors.html, _smoke_swimlane.json produced (presence verified)
• dump_viewer smoke runs (test passes with the call in place)
• Pre-commit gate clean (clang-format, clang-tidy, cpplint, markdownlint, ruff, pyright, check-headers, etc.)
• CI ubuntu + macOS sim smokes green
• Self-hosted a2a3 onboard smokes green (or warning if graphviz unavailable on the runner)

Follow-up to #769.

[gemini-code-assist]

Code Review

This pull request introduces a smoke testing utility in simpler_setup/tools/_smoke.py designed to verify that DFX capture pipeline tools can successfully parse schemas. These smoke tests have been integrated into several scene tests, including those for deps_to_graph, swimlane_converter, and dump_viewer. The reviewer suggested improving the robustness of the run_tool function by explicitly handling subprocess.TimeoutExpired to capture output during timeouts, and recommended removing Path from the __all__ export to maintain a cleaner public API.