fix(test-studio): return partial result instead of raising when metrics not cached (#358)

[rstrahan]

Summary

Fixes #358. The getTestRun resolver (nested/appsync/src/lambda/test_results_resolver/index.py, get_test_results()) raised an unhandled ValueError:

Test run … processing completed, evaluating results

when a test run reached a terminal processing state but the evaluation-aggregation step never cached testRunResult. This happens when aggregation is still running, timed out, or failed silently on a large run (the reporter hit it with 3 463 documents). The exception surfaced as an opaque error and the run spun on "Loading…" forever in Test Studio.

Change

Instead of raising when testRunResult is missing, return a structured partial TestRun — the true status, file counts, and metadata, with the metric fields omitted. The GraphQL TestRun type already declares every metric field nullable (only testRunId, status, and filesCount are non-null), so the partial response is schema-valid and the UI renders the in-progress/terminal state instead of erroring.

Side benefit: compareTestRuns calls get_test_results() per run, so previously a single not-yet-aggregated run would raise and fail the entire comparison. It now contributes a partial entry.

Scope / follow-up

This PR addresses the resolver-error half of the issue (the user-facing breakage). The issue's second point — investigating why aggregation can stall on very large runs (possible Lambda 15-min timeout) — is a separate, deeper investigation and is intentionally out of scope here; left as a documented follow-up.

Testing

Added a regression test in lib/idp_common_pkg/tests/unit/test_results_resolver.py that drives get_test_results() with a terminal-status run whose metadata has no testRunResult, asserting it returns a partial dict (true status + counts + metadata) rather than raising.

$ pytest tests/unit/test_results_resolver.py -q
8 passed

Risk

Low. Replaces a raise with a structured return on a path that was already a hard error; no behavior change on the success (cached-metrics) path.

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