v0.9.0: Runware FLUX.1 schnell as default image provider

New Runware image backend at ~$0.0006/image (FLUX.1 schnell) — 65× cheaper
than Gemini 2.5 Flash Image. Provider mirrors OpenRouter's split: interface
+ provider + support + pricing + batch, all under the 300-line cap. Batch
class uses curl_multi for true parallel A/B dispatch — wall-clock drops to
the slowest single image instead of the sum.

Changes:
- Add PRAutoBlogger_Runware_Image_Provider + Pricing + Support + Batch
- Flip PRAUTOBLOGGER_DEFAULT_IMAGE_PROVIDER/MODEL to runware:100@1
- Add prautoblogger_runware_api_key settings field (encrypted at rest)
- v0.9.0 one-time migration flips legacy default model + re-derives provider
- Wire runware branch into Image_Pipeline::create_default_provider()
- Add runware:100@1 and runware:101@1 to Image_Model_Registry (defaults top)
- Update image prompt builder: no more anthropomorphized molecules;
  prefer concrete human-scale scenes (gym bros, doctors, scientists)
- ARCHITECTURE.md + CHANGELOG.md updated with new integration + decision
- Unit tests for pricing, support, provider; update model registry test

Cost impact at 100 images/day (50 articles × A/B):
- Before (Gemini via OpenRouter): $3.90/day ≈ $117/mo
- After  (FLUX schnell via Runware): $0.06/day ≈ $1.80/mo
Net saving: ~$115/mo

includes/core/class-image-prompt-builder.php

@@ -31,12 +31,13 @@ You are a comedy writer and single-panel cartoon creator, like Gary Larson (The
 
 Given an article title and summary about peptides, supplements, or biohacking, create a SINGLE-PANEL COMIC concept. Output TWO parts separated by a blank line:
 
-SCENE: One sentence describing the visual gag — a funny, absurd, or ironic situation related to the article's topic. Use anthropomorphized molecules, lab-coat-wearing animals, befuddled scientists, gym bros encountering peptide science, supplement bottles with personality, or everyday situations with a peptide twist. Keep it simple — one clear visual joke, 1-3 characters max.
+SCENE: One sentence describing the visual gag — a funny, absurd, or ironic situation related to the article's topic. Favor CONCRETE, HUMAN-SCALE scenes: people reacting to things, doctors and patients, scientists in a lab, gym bros with peptide vials, partners at a kitchen table, ordinary objects in ordinary rooms. Keep it simple — one clear visual joke, 1-3 characters max.
 
 CAPTION: A short, punchy caption or speech bubble line (under 15 words) that delivers the punchline. The humor should be dry, nerdy, and accessible — the reader should chuckle even if they only half-understand the science.
 
 Rules:
 - The joke MUST relate to the article's actual subject matter, not generic science humor
+- DO NOT personify molecules, peptides, hormones, proteins, or other chemical structures (no "anthropomorphic molecule", no "cartoon hormone"). Image models render anthropomorphized chemistry as incoherent blobs. If the article is about a substance, show a PERSON reacting to or using the substance; if the article is abstract (a mechanism, a process, a concept), fall back on a human observer reacting to its effect.
 - Characters can have simple cartoon faces (round heads, dot eyes, expressive eyebrows)
 - Keep the scene physically simple — few objects, clear staging, easy to read at thumbnail size
 - The caption should work as a standalone joke even without the image
@@ -44,9 +45,9 @@ Rules:
 - Output ONLY the scene and caption. No preamble, no explanation.
 
 Example output format:
-A muscular gym bro stares in confusion at a tiny vial while a peptide molecule with arms and legs flexes next to him, clearly outperforming him.
+A muscular gym bro stares, deflated, at a tiny glass vial in his hand while his friend squats a barbell effortlessly in the background.
 
-"I've been doing this wrong for three years."
+"They told me the peptide did the work, not the squats."
 PROMPT;
 
 	/**