refactor(pages): remove inline prompts from A/B test AI calls

Remove inline instruction prompts from experiment generation and analysis. These instructions are now defined in ABTestGeneratePlugin and ABTestAnalyzePlugin, eliminating duplication and improving maintainability.

services/pages/analysis.go

@@ -81,19 +81,6 @@ func AnalyzeExperiment(ctx context.Context, exp *pages_model.PageExperiment) (*A
 		Context: map[string]string{
 			"experiment": string(experimentJSON),
 			"variants":   string(variantsJSON),
-			"instruction": `Analyze these A/B test results. Look at conversion rates,
-impression counts, and event distributions across variants.
-Determine if there is a statistically significant winner.
-Return valid JSON:
-{
-  "status": "winner" or "needs_more_data" or "no_difference",
-  "winner_variant_id": <ID of winning variant, or 0>,
-  "confidence": <0.0 to 1.0>,
-  "summary": "Brief human-readable summary of results",
-  "recommendation": "What to do next"
-}
-Require at least 100 impressions per variant before declaring a winner.
-Use a minimum 95% confidence threshold.`,
 		},
 	})
 	if err != nil {

services/pages/experiment.go

@@ -96,23 +96,6 @@ func GenerateExperiment(ctx context.Context, repo *repo_model.Repository, config
 			"landing_config":   string(configJSON),
 			"repo_name":        repo.Name,
 			"repo_description": repo.Description,
-			"instruction": `Analyze this landing page config and create an A/B test experiment.
-Return valid JSON with this exact structure:
-{
-  "name": "Short experiment name",
-  "variants": [
-    {
-      "name": "Variant A",
-      "config_override": { ... partial landing config fields to override ... },
-      "weight": 50
-    }
-  ]
-}
-Focus on high-impact changes: headlines, CTAs, value propositions.
-Keep variants meaningfully different but plausible.
-The control variant (original config) is added automatically — do NOT include it.
-Return 1-3 variants. Each variant's config_override should be a partial
-LandingConfig with only the fields that differ from the control.`,
 		},
 	})
 	if err != nil {