Add actionable system health recommendations

[mehul0810]

Summary

• add a read-only System Health report to Site Inventory
• explain PHP/runtime limits, OPcache, persistent object cache, database, safe HTTP/server hints, uploads, and debug logging in plain language
• classify signals as Good, Review, Action recommended, or Unavailable
• keep the payload per-site and exclude paths, credentials, request data, log contents, and private configuration values
• document the contract and extend hosted responsive smoke proof

Safety and compatibility

• no server configuration is changed
• no external requests or telemetry
• no log file or log path is read
• upload paths and full server software strings are not exposed
• multisite reports the current site/shared runtime without enumerating sites
• filtered values are normalized and hard-capped

Validation

• composer test: 121 tests / 358 assertions
• composer phpstan: pass
• composer lint: 78 PHP files pass
• scoped PHPCS: pass
• JS unit tests: 28/28
• JS lint: pass
• CSS lint: pass
• production frontend build: pass
• read-only Studio runtime proof on WordPress 7.0.3 / PHP 8.2 produced nine bounded signals and no private paths

Closes #183

[github-actions]

WordPress Playground Preview

The changes in this pull request can previewed and tested using a WordPress Playground instance.

[mehul0810]

Hosted validation is green on head 712fc487c3d4fc3bb1e02747bdca2bd3f4806652.

Proof review:

• Run 31457585760 passed the complete WordPress smoke suite.
• Desktop and 390px Site Inventory artifacts were manually reviewed.
• System Health remains compact and readable in the desktop two-column layout.
• Mobile stacks every signal, value, status, and recommendation without document overflow.
• The page visibly distinguishes measured local facts from recommendations and keeps the privacy boundary explicit.

All required hosted checks passed: code style, frontend lint/build, PHP lint 8.1-8.3, PHPUnit 8.1-8.3, security, static analysis, Playground packaging, and WordPress smoke.