refactor: system prompt sections + docs/tests

src/agents/system-prompt.test.ts

@@ -23,6 +23,30 @@ describe("buildAgentSystemPrompt", () => {
     expect(prompt).not.toContain("Owner numbers:");
   });
 
+  it("omits extended sections in minimal prompt mode", () => {
+    const prompt = buildAgentSystemPrompt({
+      workspaceDir: "/tmp/clawd",
+      promptMode: "minimal",
+      ownerNumbers: ["+123"],
+      skillsPrompt:
+        "<available_skills>\n  <skill>\n    <name>demo</name>\n  </skill>\n</available_skills>",
+      heartbeatPrompt: "ping",
+      toolNames: ["message", "memory_search"],
+      extraSystemPrompt: "Subagent details",
+    });
+
+    expect(prompt).not.toContain("## User Identity");
+    expect(prompt).not.toContain("## Skills");
+    expect(prompt).not.toContain("## Memory Recall");
+    expect(prompt).not.toContain("## Reply Tags");
+    expect(prompt).not.toContain("## Messaging");
+    expect(prompt).not.toContain("## Silent Replies");
+    expect(prompt).not.toContain("## Heartbeats");
+    expect(prompt).toContain("## Subagent Context");
+    expect(prompt).not.toContain("## Group Chat Context");
+    expect(prompt).toContain("Subagent details");
+  });
+
   it("adds reasoning tag hint when enabled", () => {
     const prompt = buildAgentSystemPrompt({
       workspaceDir: "/tmp/clawd",