Add bounded scheduled task diagnostics

[mehul0810]

Closes #143.

Summary

• adds an opt-in, read-only Scheduled Tasks diagnostic tab
• reports bounded WP-Cron pressure signals, overdue work, near-term clustering, and frequent hooks without exposing task arguments or payload data
• stores a per-site snapshot for one hour with nonce/capability-protected refresh and clear actions
• explains DISABLE_WP_CRON accurately without claiming an external runner is configured
• adds responsive admin UI, documentation, unit coverage, and hosted browser proof

Safety

• no scheduled task is run, deleted, rescheduled, or otherwise mutated
• scans at most 5,000 event instances and reports at most 20 aggregate hook rows
• no hook arguments, URLs, nonces, credentials, or user data are collected
• clear removes only Perform's diagnostic snapshot

Validation

• composer test — 126 tests, 389 assertions
• composer lint — 81 PHP files
• composer phpstan
• npm run test:js — 31 tests
• npm run lint:js
• npm run lint:css
• scoped PHPCS
• npm run build
• git diff --check

Hosted Playwright proof covers desktop/mobile layout, manual audit and clear flows, privacy/read-only copy, horizontal overflow, and lower-privilege denial.

[github-actions]

WordPress Playground Preview

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