feat(prometheus): add GPT-5.2 optimized prompt with model-based routing

- Create gpt.ts with XML-tagged, principle-driven prompt (Codex plan mode style)
- Add getPrometheusPrompt() routing: GPT models → GPT prompt, others → default
- Promote gpt-5.2 (high) to #2 in prometheus fallback chain
- Follow Atlas GPT variant pattern (isGptModel detection)

src/plugin-handlers/prometheus-agent-config-builder.ts

@@ -1,5 +1,5 @@
 import type { CategoryConfig } from "../config/schema";
-import { PROMETHEUS_PERMISSION, PROMETHEUS_SYSTEM_PROMPT } from "../agents/prometheus";
+import { PROMETHEUS_PERMISSION, getPrometheusPrompt } from "../agents/prometheus";
 import { resolvePromptAppend } from "../agents/builtin-agents/resolve-file-uri";
 import { AGENT_MODEL_REQUIREMENTS } from "../shared/model-requirements";
 import {
@@ -69,7 +69,7 @@ export async function buildPrometheusAgentConfig(params: {
     ...(resolvedModel ? { model: resolvedModel } : {}),
     ...(variantToUse ? { variant: variantToUse } : {}),
     mode: "all",
-    prompt: PROMETHEUS_SYSTEM_PROMPT,
+    prompt: getPrometheusPrompt(resolvedModel),
     permission: PROMETHEUS_PERMISSION,
     description: `${(params.configAgentPlan?.description as string) ?? "Plan agent"} (Prometheus - OhMyOpenCode)`,
     color: (params.configAgentPlan?.color as string) ?? "#FF5722",