fix(serve-mode): use resolved orchestrator prompt instead of rebuilding default

The serve-mode chat.system.transform hook always rebuilt the default
prompt via buildOrchestratorPrompt(), ignoring custom replacement
prompts loaded from orchestrator.md. This caused replacement prompts to
be appended instead of replacing the default.

Now reads the already-resolved prompt from agentDefs[0].config.prompt
(which has custom replace/append applied via resolvePrompt at agent
creation time). Falls back to buildOrchestratorPrompt() only if the
resolved prompt is missing.

Fixes #295

src/index.ts

@@ -1,5 +1,6 @@
 import type { Plugin } from '@opencode-ai/plugin';
 import { createAgents, getAgentConfigs, getDisabledAgents } from './agents';
+import { buildOrchestratorPrompt } from './agents/orchestrator';
 import { BackgroundTaskManager, MultiplexerSessionManager } from './background';
 import { loadPluginConfig, type MultiplexerConfig } from './config';
 import { parseList } from './config/agent-mcps';
@@ -550,6 +551,8 @@ const OhMyOpenCodeLite: Plugin = async (ctx) => {
     // Inject orchestrator system prompt for serve-mode sessions.
     // In serve mode, the agent's prompt field may be absent from the agents registry
     // (built before plugin config hooks run). This hook injects it at LLM call time.
+    // Uses the already-resolved prompt from agentDefs (which has custom replacement
+    // or append prompts applied) instead of rebuilding the default.
     'experimental.chat.system.transform': async (
       input: { sessionID?: string },
       output: { system: string[] },
@@ -565,14 +568,15 @@ const OhMyOpenCodeLite: Plugin = async (ctx) => {
             s.includes('orchestrator'),
         );
         if (!alreadyInjected) {
-          // Prepend the orchestrator prompt to the system array
-          // Use buildOrchestratorPrompt with disabledAgents so the
-          // serve-mode prompt matches the interactive-mode prompt
-          const { buildOrchestratorPrompt } = await import(
-            './agents/orchestrator'
-          );
-          const disabledAgents = getDisabledAgents(config);
-          const orchestratorPrompt = buildOrchestratorPrompt(disabledAgents);
+          // Prepend the orchestrator prompt to the system array.
+          // agentDefs[0] is always the orchestrator — use its resolved prompt
+          // (which includes any custom replacement or append from orchestrator.md / orchestrator_append.md)
+          // Fall back to buildOrchestratorPrompt only if the resolved prompt is missing.
+          const orchestratorDef = agentDefs[0];
+          const orchestratorPrompt =
+            typeof orchestratorDef?.config?.prompt === 'string'
+              ? orchestratorDef.config.prompt
+              : buildOrchestratorPrompt(getDisabledAgents(config));
           output.system[0] =
             orchestratorPrompt +
             (output.system[0] ? `\n\n${output.system[0]}` : '');