feat(models): OpenRouter model registry + interface + cron wiring (model-picker commit 1) (#13)

Foundation for the smart model picker. Fetches, normalizes, and caches
the OpenRouter model list (/api/v1/models — free, unauthenticated).
Daily refresh via the existing prautoblogger_daily_generation cron with
12h idempotency. 3-retry exponential backoff on transient failures;
serves last-good option payload when stale-and-fetch-fails.

New files:
- interface-model-registry.php — Phase 3-aware contract (94 lines)
- class-openrouter-model-registry.php — fetch + cache + query (226 lines)
- class-openrouter-model-normalizer.php — raw → standardized (114 lines)

Zero-coupling: no PRAUTOBLOGGER_* constants inside the service classes.
Config injected via constructor. Phase 2 lift into a shared Composer
package requires only namespace rename, zero internal edits.

Cost impact: $0/month (free endpoint, no LLM tokens).

Agent-Session: cowork-2026-04-16-model-picker-commit1

Co-authored-by: peptiderepo <peptiderepo@users.noreply.github.com>

ARCHITECTURE.md

@@ -139,6 +139,12 @@ prautoblogger/
 │   │   ├── class-cloudflare-image-support.php   # Token, account, URL, and log helpers for the CF provider
 │   │   └── (new providers go here — see CONVENTIONS.md)
 │   │
+│   ├── services/
+│   │   ├── interface-model-registry.php           # Contract for provider-specific model registries
+│   │   ├── class-openrouter-model-registry.php    # Fetches, caches, queries the OpenRouter model list
+│   │   ├── class-openrouter-model-normalizer.php  # Maps raw OpenRouter data → standardized record shape
+│   │   └── (Phase 3: class-cloudflare-workers-ai-model-registry.php)
+│   │
 │   ├── frontend/
 │   │   └── class-posts-widget.php     # [prautoblogger_posts] shortcode + REST endpoint
 │   │
@@ -347,6 +353,8 @@ All prefixed with `prautoblogger_`:
 | `prautoblogger_cloudflare_account_id`  | Cloudflare account UUID (plaintext — identifier, not secret) |
 | `prautoblogger_image_model`            | Image model alias: `flux-1-schnell` (default) or `flux-1-dev` |
 | `prautoblogger_image_style_suffix`     | Text appended to every image prompt (default: CEO-locked 90s infomercial prompt) |
+| `prautoblogger_openrouter_model_registry` | Normalized OpenRouter model list (JSON array, daily refresh, serves as durable cache) |
+| `prautoblogger_openrouter_model_registry_fetched_at` | Unix timestamp of last successful model registry refresh |
 
 ### Post Meta
 
@@ -425,6 +433,10 @@ Each pipeline execution generates a UUID (`run_id`) that tags every `prab_genera
 ### #14: Reddit RSS replaces PullPush.io (and earlier Reddit OAuth)
 Reddit rejected our OAuth API application (April 2026). We initially switched to PullPush.io, but its index was frequently stale or unavailable. Reddit's RSS/Atom feeds (`/r/{sub}/hot.rss`) proved the most reliable option — they work from datacenter IPs where .json gets 403, require no auth, and have no apparent rate limit. The .json endpoints are kept as a fallback for posts and as the sole source for comment data. Each collected item's metadata includes a `data_source` field (`reddit_rss` or `reddit_json`) for auditability.
 
+### #18: OpenRouter model registry — daily refresh, WP option + transient cache, zero-coupling
+
+The admin model picker (v1) needs to list OpenRouter models with pricing and capabilities. We fetch `https://openrouter.ai/api/v1/models` (free, unauthenticated) once daily and store the normalized payload in a WP option fronted by a 24h transient. On stale-and-fetch-fails, we serve last-good + surface a warning. The registry class (`class-openrouter-model-registry.php`) takes all config via constructor (option name, transient name, endpoint URL) — no PRAUTOBLOGGER_* constants inside the class body. Phase 2 lifts it into a shared Composer package with zero internal edits. Phase 3 adds a parallel `Cloudflare_WorkersAI_Model_Registry` behind the same interface. Capability vocabulary: `text→text`, `text+image→text`, `text+audio→text`, `text→image`, `text→audio`, `text→video`, `text→embedding`. Cost: $0/month.
+
 ### #16: Image generation via Cloudflare Workers AI (FLUX.1), direct (not via AI Gateway)
 The image-generation layer (started 2026-04-15, tracked in `convo/prautoblogger/threads/2026-04-image-pipeline/`) uses FLUX.1 [schnell] on Cloudflare Workers AI as its default model, chosen for its ~$0.0011/MP cost and 2–3 sec latency. FLUX.1 [dev] is a ~4× cost upgrade exposed as a dropdown for specific posts that warrant it. Calls go directly to `https://api.cloudflare.com/client/v4/accounts/{id}/ai/run/@cf/black-forest-labs/...`, *not* through the Cloudflare AI Gateway that we use for OpenRouter — the gateway route to Workers AI currently 403s (pre-existing open issue). The provider lives behind `PRAutoBlogger_Image_Provider_Interface`, so the decision is trivially reversible: switching to a different image API (DALL-E, Replicate, a future AI Gateway route) is a new class implementation plus a one-line swap in the pipeline wiring. Trade-off: we run two different Cloudflare integration paths (gateway for OpenRouter LLMs, direct for Workers AI images) until the gateway route stabilizes — minor cognitive overhead, zero functional downside.