fix: resolve Logger access, wrong model name, and API key guard tests

- bootstrap: add PRAUTOBLOGGER_MAX_RETRIES, API_TIMEOUT, RETRY_BASE_DELAY constants
- BaseTestCase: add wp_json_encode + home_url stubs, reset Logger singleton in tearDown
- CostTrackerTest: use openai/gpt-4o (in MODEL_PRICING), fix log_api_call args,
  allow multiple wpdb inserts (Logger may also insert event_log rows)
- OpenRouterPricingTest: add wpdb mock with prefix for Logger access on unknown models
- OpenRouterProviderTest: test send_chat_completion throws RuntimeException when
  no API key is configured (matches actual guard clause behavior)

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

tests/bootstrap.php

@@ -29,6 +29,17 @@ if ( ! defined( 'HOUR_IN_SECONDS' ) ) {
     define( 'HOUR_IN_SECONDS', 3600 );
 }
 
+// Plugin constants used by OpenRouter provider retry logic.
+if ( ! defined( 'PRAUTOBLOGGER_MAX_RETRIES' ) ) {
+    define( 'PRAUTOBLOGGER_MAX_RETRIES', 3 );
+}
+if ( ! defined( 'PRAUTOBLOGGER_API_TIMEOUT_SECONDS' ) ) {
+    define( 'PRAUTOBLOGGER_API_TIMEOUT_SECONDS', 30 );
+}
+if ( ! defined( 'PRAUTOBLOGGER_RETRY_BASE_DELAY_SECONDS' ) ) {
+    define( 'PRAUTOBLOGGER_RETRY_BASE_DELAY_SECONDS', 1 );
+}
+
 // WordPress database constants used in $wpdb queries.
 if ( ! defined( 'ARRAY_A' ) ) {
     define( 'ARRAY_A', 'ARRAY_A' );