Q78: GitHub Copilot turns carry the agent's system instructions

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/main/services/provider-tool-turns/turns.ts

@@ -164,6 +164,7 @@ export async function runCopilotTurn(input: ProviderToolTurnInput): Promise<Agen
     tools: responsesToolDefs(input.tools),
     tool_choice: "auto",
     store: false,
+    ...(input.instructions ? { instructions: input.instructions } : {}),
   };
   const response = await postJson(`${baseUrl}/responses`, {
     Authorization: `Bearer ${access}`,