feat: v2.6.0 3-step AI pipeline, VPS worker, REST worker routes

- 3-step OpenRouter pipeline: Gatekeeper scoring/classification, PubMed+Google URL extraction, Markdown summary generation
- REST worker routes /wp-json/peptide-news/v1/worker/* with X-Peptide-News-Token auth
- Standalone Coolify worker (tools/vps-worker) with Dockerfile + docker-compose
- CLI commands, content extractor, pubmed extractor, google url resolver
- 89 PHPUnit tests passing

tools/vps-worker/README.md

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+# Peptide News Aggregator — Hybrid Shared Hosting + Coolify VPS Architecture
+
+This directory contains the **v2.6.0 Standalone VPS Worker**, designed for high-signal peptide news pipelines where WordPress is hosted on a **shared server (e.g., prepaid shared hosting)** and heavy AI/scraping processes are offloaded to a **dedicated Linux VPS running Coolify** (e.g., Hostinger KVM8).
+
+---
+
+## Why Use a Hybrid Architecture?
+
+### 1. Shared Hosting Server (WordPress + Database)
+- **Strengths**: Serves public visitors, runs WordPress admin UI, stores `wp_peptide_news_articles`, and handles lightweight web WP-Cron tasks.
+- **Limitations**:
+  - PHP execution timeouts (60-second CGI limit).
+  - Shared IP addresses may be rate-limited or blocked by Google News or NCBI/PubMed.
+
+### 2. Dedicated VPS Worker (Coolify Container / Scheduled Task)
+- **Strengths**:
+  - Uncapped execution time for OpenRouter/Gemini 3-Step AI Pipeline calls.
+  - Dedicated VPS IP address for reliable PubMed E-utilities XML fetching and Google News redirect URL resolution.
+  - Zero load on your shared WordPress server's CPU or memory during AI article generation.
+  - Effortless management using **Coolify UI** or Coolify MCP.
+
+---
+
+## How It Works
+
+```
+[Shared Hosting: WordPress Server]
+  ├── Hosts wp_peptide_news_articles & Web Admin Dashboard
+  └── REST API (/wp-json/peptide-news/v1/worker/*)
+          ▲                      ▲
+          │ 1. GET /pending      │ 3. POST /update (ai_summary, rigor_score)
+          ▼                      │
+[Coolify Instance on VPS: peptide-news-worker]
+  ├── Runs via Coolify Scheduled Task / Docker Container
+  └── Calls OpenRouter / Gemini API (3-Step Pipeline: Gatekeeper -> Extract -> Markdown Brief)
+```
+
+---
+
+## Deploying on Coolify (Step-by-Step)
+
+### Step 1: Set a Secret Token in WordPress
+1. Log into your shared WordPress site dashboard.
+2. Go to **Settings** -> **Peptide News**.
+3. Under **VPS Worker Integration**, enter a secret token (e.g. `vps_secret_token_12345`) and save.
+
+### Step 2: Deploy to Coolify as a Scheduled Task (Recommended)
+1. In your Coolify dashboard, click **+ Add Resource** -> **Application** -> select your Git repository (or use **Dockerfile** deployment).
+2. Set the **Build Pack** to `Dockerfile` (pointing to `tools/vps-worker/Dockerfile`).
+3. Under **Environment Variables**, configure:
+   - `WP_URL`: `https://your-shared-wordpress-site.com`
+   - `VPS_TOKEN`: `vps_secret_token_12345`
+   - `WORKER_ACTION`: `process-llm`
+   - `OPENROUTER_KEY`: `sk-or-v1-...`
+   - `OPENROUTER_MODEL`: `google/gemini-2.0-flash-001`
+   - `BATCH_SIZE`: `25`
+4. Under **Scheduled Tasks** (or Coolify Cron Jobs), create a new schedule:
+   - **Cron Expression**: `0 * * * *` (runs every hour)
+   - **Command**: `php /app/worker.php`
+5. Click **Deploy**. Coolify will build the lightweight Alpine PHP container and execute the job automatically on schedule.
+
+---
+
+## REST API Worker Endpoints
+
+All endpoints require either WordPress admin authentication OR a valid `X-Peptide-News-Token: <your-token>` header:
+
+- `GET /wp-json/peptide-news/v1/worker/pending?limit=20`  
+  Returns pending articles requiring AI analysis.
+- `POST /wp-json/peptide-news/v1/worker/update`  
+  Updates an article with completed AI summaries, tags, and scientific rigor scores.
+- `POST /wp-json/peptide-news/v1/worker/ingest`  
+  Bulk-ingests new articles scraped directly on the VPS into the WordPress database.