PR Vision v0.3.0: per-call cost accountability + LLM call audit trail

P0 security:
- PRV_Gateway_Client: remove response body from RuntimeException (HTTP status only)
- PRV_Capture_Writer: allowlist-only write (prompt/response text, never headers/auth)
- Mandatory capture order: can_afford → probe → persist_result → update_row_cost → write_meta → capture_io
- capture_io last and wrapped in swallowing try/catch

New tables (SCHEMA_VERSION 3):
- prv_call_meta: cost/metadata per call, kept indefinitely
- prv_call_io: rendered prompt + raw response, pruned on retention window (default 90d)

New classes:
- PRV_Call_Meta_Table, PRV_Call_Io_Table: table schema + dbDelta
- PRV_Capture_Writer: metadata + I/O write; security allowlist enforced
- PRV_Prune_Cron: daily prv_daily_prune cron deletes aged prv_call_io rows only
- PRV_Cost_Rollup_Query: MTD summary, model breakdown, drill-down, projection
- PRV_Call_Log_Query: paginated + filtered call-log query + per-call I/O fetch
- PRV_Costs_Page + PRV_Costs_Renderer: Costs admin sub-page (cap progress, bento, model table, drill-down)
- PRV_Call_Log_Page + PRV_Call_Log_Table_Renderer: Call Log admin sub-page (filter bar, paginated table, WCAG AA pagination)
- PRV_Call_Drawer_Renderer: non-modal complementary drawer (5 states: Normal/Pruned/Legacy/Failed/Loading)
- PRV_Call_Drawer_Script: inline JS for drawer (300-line split from renderer)
- PRV_Call_Detail_Ajax: wp_ajax_prv_call_detail AJAX handler
- PRV_Admin_Page_Css: CSS provider (300-line split from PRV_Admin_Page)
- PRV_Probe_Run_Executor: inner probe loop (300-line split from PRV_Probe_Runner)

Updated:
- PRV_Probe_Result: tokens_in/tokens_out params + getters
- Both providers: report tokens_in/tokens_out from usage.prompt_tokens/completion_tokens
- PRV_Probe_Runner: slimmed to lock+UUID+delegation; injects PRV_Capture_Writer
- PRV_Config: get_io_retention_days(); PRV_IO_RETENTION_DEFAULT_DAYS constant
- PRV_Upgrader/Activator/Deactivator/Plugin: register new tables, cron, pages, AJAX
- Settings: retention days field + save in controller
- uninstall.php: DROP both new tables, clear prv_daily_prune cron
- Subnav 4-tab strip (Dashboard | Costs | Call Log | Settings) on all pages
- ARCHITECTURE.md, CHANGELOG.md, CONTEXT.md, CONVENTIONS.md updated

Tests:
- test-capture-writer.php: write_meta, write_io, P0 security (401 record has no key/Bearer/sk-or-)
- test-cost-audit.php: MTD reconciliation, projection, prune, forced capture_io exception, table drops

Agent-Session: peptiderepo-geomonitor-v0.3.0-cost-audit

includes/providers/class-prv-gateway-client.php

@@ -33,6 +33,13 @@ declare(strict_types=1);
  */
 class PRV_Gateway_Client {
 
+	/**
+	 * HTTP status code from the most recent request (set on permanent error).
+	 *
+	 * @var int
+	 */
+	private int $last_http_status = 200;
+
 	/**
 	 * Base URL for the Cloudflare AI Gateway (without trailing slash).
 	 */
@@ -59,6 +66,9 @@ class PRV_Gateway_Client {
 	 * @return array<string, mixed> Decoded JSON response body.
 	 *
 	 * @throws \RuntimeException On permanent HTTP failure or parse error.
+	 *                              Exception message carries HTTP status code only;
+	 *                              the response body is never included (P0: prevents
+	 *                              secret-key leakage via 401 error responses).
 	 */
 	public function post_to_gateway( string $provider_slug, array $body, string $api_key, string $endpoint = '/chat/completions' ): array {
 		$base_url  = $this->build_base_url( $provider_slug );
@@ -110,8 +120,9 @@ class PRV_Gateway_Client {
 				}
 
 				if ( $status >= 400 ) {
-					// phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped -- exception message, not HTML output
-					throw new \RuntimeException( sprintf( 'PR Vision gateway HTTP %d: %s', $status, substr( $raw_body, 0, 300 ) ) );
+					$this->last_http_status = $status;
+					// phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped -- exception message, not HTML output; body intentionally omitted (P0: prevents key-leak via 401 body)
+					throw new \RuntimeException( sprintf( 'PR Vision gateway HTTP %d', $status ) );
 				}
 
 				$data = json_decode( $raw_body, true );
@@ -129,6 +140,18 @@ class PRV_Gateway_Client {
 		throw new \RuntimeException( sprintf( 'PR Vision: gateway failed after %d attempts. Last: %s', PRV_MAX_RETRIES, $last_error ) );
 	}
 
+	/**
+	 * Get the HTTP status code from the last failed request.
+	 *
+	 * Allows callers to record the HTTP status code in error records without
+	 * parsing the exception message. Returns 200 when no failure has occurred.
+	 *
+	 * @return int HTTP status code.
+	 */
+	public function get_last_http_status(): int {
+		return $this->last_http_status;
+	}
+
 	/**
 	 * Build the API base URL (gateway or direct fallback).
 	 *