Bound Playground custom archive cache growth

[chubes4]

Summary

• bound content-addressed custom-*.zip Playground archives by configurable age, size, and count while leaving stable WordPress release archives untouched
• protect archives with process-scoped runtime references and owner-aware locks, including shared use and crashed-process recovery
• expose deterministic diagnose/dry-run/apply maintenance evidence and attach automatic apply evidence to runtime startup cache validation
• run maintenance on startup and teardown using WP_CODEBOX_PLAYGROUND_WORDPRESS_CACHE_DIR

Defaults

• maximum age: 7 days
• maximum custom cache size: 1 GiB
• maximum custom archive count: 20
• stale legacy lock age: 10 minutes

All bounds are configurable through the documented WP_CODEBOX_PLAYGROUND_CUSTOM_ARCHIVE_* environment variables.

Testing

• npm run build
• npm run test:playground-custom-archive-cache
• npx tsx tests/playground-wordpress-release-cache.test.ts
• npx tsx tests/playground-readonly-mounts.test.ts
• npx tsx tests/playground-cli-runner-bootstrap-ini.test.ts
• npx tsx tests/preview-lease-provider.test.ts
• npm run test:production-boundary-enforcement
• git diff --check

npm run check progressed through build and the initial smoke groups, then stopped at the unchanged command-registry-smoke failure tracked in #1745: wordpress.collect-workload-result outputShape should mention outputSchema id.

Dry-run evidence

The live configured cache dry-run reported 1 custom archive (31,435,175 bytes), 0 candidates, 0 active protections, and 0 removals under the new defaults.

Fixes #1924

[chubes4]

Independent review fixes pushed in 7e09da83:

• replaced PID liveness with token-owned renewable leases carrying host, boot, PID, and process-start identity; foreign owners remain active until bounded expiry
• switched retention inspection/removal to lstat, protect symlinks and multiply-linked files, and report allocated blocks as verified reclaimed bytes
• clean orphan lock/reference sidecars without deleting active leases
• surface automatic maintenance policy/permission failures in startup evidence and bounded teardown warnings
• wired the complete unit, separate-process, and startup/teardown suite into the exact-head contracts workflow

Validation passed: build/typecheck, complete cache suite, agent-task contracts, all exact workflow contract commands, production-boundary enforcement, and existing Playground lifecycle regressions. npm run check still stops only at the unchanged failure tracked in #1745. Local actionlint was unavailable; the pushed workflow-lint check is authoritative.