feat: v0.2.2 — CI hardening, remove dead stubs, strengthen tests

Address CTO audit findings for PRAutoBlogger:
- CI pipeline now runs PHPCS (WordPress standards) and PHPUnit before deploy
- Removed TikTok/Instagram/YouTube stub providers (dead code, not registered)
- Rewrote PublisherTest with real behavioral assertions (post_status, metadata,
  taxonomy, log linking, hooks) instead of method-existence checks
- Added cross-system LLM budget coordination docs to ARCHITECTURE.md
- Bumped version to 0.2.2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/admin/class-settings-fields.php

@@ -186,9 +186,6 @@ class PRAutoBlogger_Settings_Fields {
 				'section'     => 'prautoblogger_sources',
 				'options'     => [
 					'reddit'    => __( 'Reddit (RSS + .json)', 'prautoblogger' ),
-					'tiktok'    => __( 'TikTok (coming soon)', 'prautoblogger' ),
-					'instagram' => __( 'Instagram (coming soon)', 'prautoblogger' ),
-					'youtube'   => __( 'YouTube (coming soon)', 'prautoblogger' ),
 				],
 				'default'     => '["reddit"]',
 				'description' => __( 'Select which platforms to monitor for topics.', 'prautoblogger' ),