[auto-review #1417] fix otel test collection crash + demo formatting (CI)

[Chrisclone]

Auto-review of pixeltable#1417 (otel-drafting)

Targets Chris's PR: pixeltable#1417 (base otel-drafting).

Scope of this review was CI failures + high-level architecture only. The OTEL design itself looks solid (see notes at the bottom); this PR only fixes the two CI breakages.

Issues found

1. CI failure (real bug in diff) — tests/test_otel.py crashes collection in the minimal env.
   Line 14 was _OTEL_INSTALLED = find_spec('opentelemetry.sdk') is not None. importlib.util.find_spec on a dotted name imports the parent package to read its __path__, so when opentelemetry is not installed it raises ModuleNotFoundError instead of returning None. In the minimal matrix job (no [otel] extra) this aborts collection of the whole test module:
   ModuleNotFoundError: No module named 'opentelemetry' -> Interrupted: 1 error during collection (exit 2).
   Notably, the production code already handles this exact gotcha — Env._maybe_enable_otel wraps the same call in try/except ModuleNotFoundError (pixeltable/env.py:634-641) with a comment explaining it. The test just didn't mirror it.

2. CI failure (real bug in diff) — static-checks fails on ruff format --check.
   otel_demo.py (committed at repo root) was not ruff-formatted: "Would reformat: otel_demo.py" -> exit 1. ruff check passes because it only targets pixeltable tests tool, but ruff format --check runs over the whole repo.

(The validate job failure is just the aggregate gate over the matrix; standard/ubuntu and macos passed because they install the [otel] extra. No separate fix needed.)

Changes made

• tests/test_otel.py: extracted a small _otel_installed() helper that wraps find_spec('opentelemetry.sdk') in try/except ModuleNotFoundError, mirroring the env.py guard. Behavior is unchanged when the extra is installed.
• otel_demo.py: applied ruff format (one line recombined). No logic change.

Validated locally

• ruff format --check -> "469 files already formatted" (clean).
• ruff check pixeltable tests tool and ruff check --select I -> "All checks passed!".
• python -m py_compile tests/test_otel.py otel_demo.py -> OK.
• Reproduced the original crash and confirmed the guard fixes it: find_spec('absent_pkg.sub') raises ModuleNotFoundError; the wrapped helper returns False.
• Could not run the otel pytest suite locally — this base env has no built pixeltable._version (package not pip-installed), so import pixeltable fails at collection regardless of the change. The fix is purely import-time, exercised by the reproduction above; it should be confirmed by the minimal CI job on re-run.

False-positive risk / what to sanity-check

• Low risk overall — both changes are mechanical and mirror existing in-repo patterns. The test fix only changes the no-extra code path (returns False instead of raising); when opentelemetry is installed it behaves exactly as before, so the otel tests still run on standard/macos.
• Not addressed (flagging, not fixing): otel_demo.py and OTEL_PLAN.md live at the repo root, and otel_demo.py imports _double from tests.test_hooks (a demo depending on the test suite). For a draft that's fine, but you'll probably want to relocate the demo (e.g. docs/sample-apps/) and drop the plan doc / move the _double UDF out of tests/ before this merges. I left them in place since removal is a product call, not a CI fix.

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