feat(models): OpenRouter model picker + AJAX refresh + cost preview (v0.11.0 complete)

- AJAX endpoint 'prautoblogger_refresh_models' for manual model registry refresh
- Admin UI button on AI Models tab to trigger refresh (nonce + capability gated)
- Cost preview integration in field renderer using historical token averages
- New public method on Cost Tracker: get_avg_tokens_for_stages(array $stages, int $days = 30): array
- Enhanced field renderer with capability-specific cost calculation (outline+draft+polish for writing, single stage for analysis/editor)
- Autoloader updated to scan ajax/ directory for model registry refresh handler
- Admin JS enhanced with AJAX toggle handler for refresh button
- Template updated with refresh button + nonce in AI Models section
- CHANGELOG + CONVENTIONS + version bump to 0.11.0
- All files under 300-line cap, PHPCS-clean

Spec: https://github.com/peptiderepo/prautoblogger/issues/111
Open questions all resolved per seq-02 plan-ack.

CHANGELOG.md

@@ -5,6 +5,20 @@ All notable changes to PRAutoBlogger will be documented in this file.
 Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project uses [Semantic Versioning](https://semver.org/).
 
+## [0.11.0] — 2026-04-23
+
+### Added
+- **OpenRouter model picker for text models.** Admin-facing dropdown field type (`model_select`) with searchable list, capability filtering, and estimated cost preview. Replaces free-text model slug inputs on the three text model settings (analysis, writing, editor). Includes daily cron refresh of the OpenRouter registry cache and manual "Refresh Model List" button on the AI Models tab.
+
+- **Cost preview in model picker.** Shows estimated cost per generation based on historical token usage for the 30 days prior. Maps each setting to its constituent pipeline stages (writing model = outline + draft + polish).
+
+- **AJAX refresh endpoint** (`prautoblogger_refresh_models`) for manual model registry refresh with nonce + capability gating (`manage_options`).
+
+- **New public method on Cost Tracker:** `get_avg_tokens_for_stages(array $stages, int $days = 30): array` returns average input/output token counts for a stage list, used by cost preview.
+
+### Changed
+- **AI Models tab now renders a "Refresh Model List" button** next to the panel title. Triggers `prautoblogger_refresh_models` AJAX endpoint.
+
 ## [0.10.1] — 2026-04-23
 
 ### Fixed