feat: peptide-geo-monitor v0.1.0 — AI-visibility dashboard

Add initial plugin implementation per the CTO engineering handoff
(geomonitor/threads/2026-06-ai-visibility-v1/01-cto-eng-handoff.md).

## What
- PGM_Probe_Provider interface + PGM_Probe_Result value object
- PGM_Perplexity_Provider (sonar via OpenRouter/CF AI Gateway)
- PGM_OpenRouter_Provider (GPT-search + Gemini-search, generic parameterised)
- PGM_Gateway_Client: shared HTTP + exponential-backoff retry (mirrors PRAB)
- PGM_Citation_Detector: domain extraction, is_cited(), get_our_position()
- PGM_Cost_Ledger: MTD cost from DB, can_afford() pre-check, hard monthly cap
- PGM_Probe_Runner: peptides×intents×models run, budget abort, in-run cache
- PGM_Table_Manager: pgm_ai_visibility dbDelta, schema-version, drop_table()
- PGM_Config: typed getters, seed_defaults() (12 peptides, 3 intents, 3 models)
- PGM_Cron: weekly pgm_weekly_probe schedule/clear
- PGM_Data_Collector + PGM_Dashboard_Panel interfaces (seam for future panels)
- PGM_Collector_Registry: singleton registry
- PGM_Ai_Visibility_Collector: trendline, standings, MTD cost (score formula)
- PGM_Ai_Visibility_Panel: proxy note, Chart.js trendline, standings table
- PGM_Admin_Page: GEO Monitor menu, Run now POST handler (nonce+capability)
- uninstall.php: DROP TABLE + DELETE pgm_* options + wp_clear_scheduled_hook
- Unit tests (6 files): citation detection, score calc, cost ledger + budget
  abort, provider response parsing (mock HTTP), cron, uninstall purge
- ARCHITECTURE.md, CONVENTIONS.md, CONTEXT.md (score formula), README.md,
  CHANGELOG.md — same-commit per DoD
- CI workflow: PHP lint (8.1/8.2/8.3) + PHPCS + 300-line check

## Security
- Secrets from wp-config constants only; none hardcoded
- manage_options + nonce on every admin action
- Input sanitized; output escaped

Agent-Session: geomonitor v0.1.0

includes/core/class-pgm-table-manager.php

@@ -0,0 +1,94 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Database table creation and schema versioning for PGM.
+ *
+ * Creates {prefix}pgm_ai_visibility via dbDelta (idempotent). Tracks the
+ * schema version in the pgm_schema_version option so future migrations can
+ * detect when an upgrade is needed without destructive ALTER TABLE.
+ *
+ * Who triggers: PGM_Activator::activate() on plugin activation.
+ * Dependencies: $wpdb global, dbDelta() (requires upgrade.php).
+ *
+ * @see class-pgm-activator.php — Calls create_table() on activation.
+ * @see ARCHITECTURE.md         — §Storage.
+ * @package PeptideGeoMonitor
+ */
+class PGM_Table_Manager {
+
+	/**
+	 * Name of the custom table (without $wpdb->prefix).
+	 */
+	const TABLE_BASE = 'pgm_ai_visibility';
+
+	/**
+	 * Create or upgrade the AI-visibility table.
+	 *
+	 * Uses dbDelta to create or non-destructively alter the table.
+	 * Records the schema version in an option afterwards.
+	 *
+	 * Side effects: Writes to the database; sets pgm_schema_version option.
+	 *
+	 * @return void
+	 */
+	public static function create_table(): void {
+		global $wpdb;
+
+		$table_name      = $wpdb->prefix . self::TABLE_BASE;
+		$charset_collate = $wpdb->get_charset_collate();
+
+		$sql = "CREATE TABLE {$table_name} (
+			id          BIGINT(20) UNSIGNED NOT NULL AUTO_INCREMENT,
+			run_id      VARCHAR(36)         NOT NULL,
+			captured_at DATETIME            NOT NULL,
+			peptide_slug   VARCHAR(200)     NOT NULL,
+			peptide_label  VARCHAR(200)     NOT NULL,
+			model          VARCHAR(200)     NOT NULL,
+			prompt_intent  VARCHAR(200)     NOT NULL,
+			cited          TINYINT(1)       NOT NULL DEFAULT 0,
+			our_position   INT(11)          NULL     DEFAULT NULL,
+			source_domains LONGTEXT         NOT NULL DEFAULT '',
+			raw_excerpt    LONGTEXT         NOT NULL DEFAULT '',
+			cost_usd       DECIMAL(12,8)    NOT NULL DEFAULT 0.00000000,
+			PRIMARY KEY (id),
+			KEY run_id (run_id),
+			KEY peptide_slug (peptide_slug),
+			KEY captured_at (captured_at)
+		) {$charset_collate};";
+
+		if ( ! function_exists( 'dbDelta' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/upgrade.php';
+		}
+
+		dbDelta( $sql );
+
+		update_option( 'pgm_schema_version', PGM_SCHEMA_VERSION );
+	}
+
+	/**
+	 * Get the full table name including the WP prefix.
+	 *
+	 * @return string
+	 */
+	public static function get_table_name(): string {
+		global $wpdb;
+		return $wpdb->prefix . self::TABLE_BASE;
+	}
+
+	/**
+	 * Drop the AI-visibility table entirely.
+	 *
+	 * Called only from uninstall.php — never during normal deactivation.
+	 *
+	 * Side effects: Permanently destroys all probe data.
+	 *
+	 * @return void
+	 */
+	public static function drop_table(): void {
+		global $wpdb;
+		$table = $wpdb->prefix . self::TABLE_BASE;
+		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.SchemaChange, WordPress.DB.PreparedSQL.InterpolatedNotPrepared
+		$wpdb->query( "DROP TABLE IF EXISTS {$table}" );
+	}
+}