add durable Unity test run contracts

[niqibiao]

Summary

• add a focused tests domain with core tests/run and tests/status contracts
• validate mode, optional exact test names, array bounds, UTF-16 item length, runId, and wait range before HTTP dispatch
• require the package's test_runs_v1 capability before claiming an invocation
• mark tests/run direct-only so invalid batch requests fail locally without creating an outbox record or network request
• add tests-only lifecycle guidance for recovering the same deterministic runId after a reload instead of starting a replacement run

Impact

A complex workflow can start one Unity Test run and use tests/status(waitSeconds=10) to wait for progress in fewer round trips. This reduces repeated polling output, token use, and context churn while preserving the same run identity across Unity reloads and uncertain acceptance responses.

Validation

• focused batch and non-command capability preflight checks passed
• offline tests-domain discovery returns exactly the two core contracts
• live Unity 2022 registry and test_runs_v1 capability verified against companion package PR
• live Edit Mode, Play Mode, long-poll, history, dirty-scene, replay, and uppercase runId workflows passed
• local uncommitted suite: 50/51 passed; the only failure is PR Improve Unity command discovery and preflight #12's existing command-reference context-budget assertion, whose unrelated trim was deliberately removed from this PR
• Python/JSON syntax and git diff --check passed
• per scope, no test/eval/report files are included in this PR

Stack

• base: codex/console-get (PR Add bounded Unity console diagnostics contract #14)
• requires package support from unity-csharpconsole PR #8
• PR Improve Unity command discovery and preflight #12 command-discovery token/context optimization remains unchanged and will be fixed and re-tested in a separate PR