fix: preserve WebView acquisition ownership (#3252)

Keep evicted OpenAI WebView acquisitions from displacing their replacements,
and retain one-shot lease cleanup independently of the cache.

Replace scheduler-count dashboard test readiness with bounded observation,
contain owned Swift test processes before retries, and avoid atomic writes
when seeding private performance corpora before readers exist.

Bind macOS descendant cleanup signals to process generations through the
native audit-token API, preserving normal signal permissions.

Preserve existing scanner workloads, assertions, and suite deadlines.

Wait for meaningful Claude fixture responses and observed process readiness
instead of PTY-idle or fixed-sleep assumptions in functional tests.

Seed adaptive test configurations before settings initialization, preserving
disabled providers and web access without replaying per-provider writes.