feat(phase2b): P2b.4 — tier routing + Authority pipeline + citation/imagery gates (#181, v0.31.0)

Authority_Pipeline orchestrator (research→curate→draft→editorial→seo→publish gate) + per-category tier router behind master flag prautoblogger_authority_pipeline_enabled (DEFAULT OFF — zero behavior change until enabled). Cost-ceiling halts→hold; citation + imagery gates. QA APPROVE b086079; CI green (phpcs+phpunit VPS-verified).

Agent-Session: prab-phase2b-4-merge

includes/core/class-tier-router.php

@@ -0,0 +1,100 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
+ *
+ * Per-category generation tier router for the Authority pipeline.
+ *
+ * What: Resolves whether a given article idea should enter the Authority
+ *       pipeline or fall through to the Economy single-pass. The master
+ *       switch (`prautoblogger_authority_pipeline_enabled`) defaults FALSE,
+ *       which guarantees byte-identical behaviour to today — no articles
+ *       ever touch the Authority path unless an operator explicitly enables
+ *       the flag. When the flag is ON, per-category overrides in
+ *       `prautoblogger_category_tiers` demote specific categories to
+ *       Economy; every other category (unclassified, new, missing) stays
+ *       at the Authority default.
+ *
+ * Who triggers it: PRAutoBlogger_Article_Worker::generate() (P2b.4).
+ * Dependencies: WordPress get_option(), PRAutoBlogger_Article_Idea.
+ *
+ * @see providers/interface-tier-router.php    — Interface this class implements.
+ * @see core/class-article-worker.php          — Call site (3-line tier check).
+ * @see core/class-authority-pipeline.php      — Authority path executed on 'authority'.
+ * @see ARCHITECTURE.md                        — Phase 2b tier routing.
+ */
+class PRAutoBlogger_Tier_Router implements PRAutoBlogger_Tier_Router_Interface {
+
+	/** Option key for the master Authority pipeline feature flag. */
+	public const OPTION_MASTER_FLAG = 'prautoblogger_authority_pipeline_enabled';
+
+	/** Option key for the per-category tier map (serialized array). */
+	public const OPTION_CATEGORY_TIERS = 'prautoblogger_category_tiers';
+
+	/** Default tier when a category has no explicit override: Authority. */
+	private const DEFAULT_TIER = 'authority';
+
+	/**
+	 * Resolve the generation tier for an article idea.
+	 *
+	 * Returns 'economy' immediately when the master flag is OFF — this is
+	 * the production default and must guarantee zero behaviour change
+	 * relative to the pre-P2b.4 codebase.
+	 *
+	 * When the master flag is ON, looks up the idea's article_type in the
+	 * per-category tier map. Values of 'economy' explicitly demote that
+	 * category. Any other value, or no entry at all, keeps the Authority
+	 * default.
+	 *
+	 * Side effects: two get_option() calls (cached by WordPress object cache).
+	 *
+	 * @param PRAutoBlogger_Article_Idea $idea The article idea to route.
+	 * @return string 'authority' or 'economy'
+	 */
+	public function resolve( PRAutoBlogger_Article_Idea $idea ): string {
+		if ( ! $this->is_master_flag_on() ) {
+			return 'economy';
+		}
+
+		return $this->resolve_from_category( $idea->get_article_type() );
+	}
+
+	// ── Private helpers ──────────────────────────────────────────────────
+
+	/**
+	 * Whether the Authority pipeline master switch is enabled.
+	 *
+	 * The option defaults to false (disabled). Operators must explicitly
+	 * set it to '1' or true via wp_options / WP admin to enable the path.
+	 *
+	 * @return bool
+	 */
+	private function is_master_flag_on(): bool {
+		$flag = get_option( self::OPTION_MASTER_FLAG, false );
+		return in_array( $flag, array( '1', true, 1 ), true );
+	}
+
+	/**
+	 * Resolve tier from the per-category tier map.
+	 *
+	 * The map is a serialized PHP array (stored via WordPress options) of
+	 * `['category_slug' => 'economy']`. Only 'economy' is a meaningful
+	 * explicit value — anything else (including 'authority') is treated
+	 * as "keep the default".
+	 *
+	 * Unrecognised or empty maps → default Authority tier (additive safety).
+	 *
+	 * @param string $article_type Article type / category slug from the idea.
+	 * @return string 'authority' or 'economy'
+	 */
+	private function resolve_from_category( string $article_type ): string {
+		$raw = get_option( self::OPTION_CATEGORY_TIERS, array() );
+		$map = is_array( $raw ) ? $raw : array();
+
+		$tier = $map[ $article_type ] ?? self::DEFAULT_TIER;
+
+		// Only 'economy' is a valid explicit demote; any other value defaults.
+		return 'economy' === $tier ? 'economy' : 'authority';
+	}
+}