refactor: rombak arsitektur file ke modular clean-arch (vertikal per-feature)

Organisasi ulang layer-first (domain/application/infrastructure) menjadi
vertikal per-feature, behavior tidak berubah:

- src/shared/domain/  -> fondasi bersama (ex-domain/core): message, provider,
  tool_call, tool_result, store, error, usage, conversation
- src/features/agent/ -> LLM turn loop: domain (TurnEvent, AgentTurnParams) +
  application (turn_service, ports) + infrastructure (llm LlmClient + tools)
- src/features/cms/   -> settings/conversation/memory persistence: domain +
  application (services) + infrastructure (persistence repos)
- src/features/subagent/ -> orchestration: domain (AccessTier) + infrastructure
  (engine runner, context, provider, delegate, spawn_tools)
- src/features/workflow/ -> multi-phase + hive-mind: domain + infrastructure
- src/interfaces/     -> cli + tui (outer ring) tetap

Subagent-runner (engine.ts runAgent, division.ts toolsFor) dipindah ke
features/subagent (bukan agent tools) utk memutus coupling agent<->subagent.

Alias tsconfig: @zesdex/domain -> shared/domain, + @zesdex/agent,
@zesdex/agent-infra, @zesdex/cms, @zesdex/subagent, @zesdex/workflow, @zesdex/shared.
Bersihkan dead: application/ports PasswordService/TokenService/AuthService.
compose.ts (composition root) & bootstrap repoint ke barrel feature.

Gates: tsc --noEmit 0 error, bun test 70 pass/0 fail, bun build 147 modules,
./dist/zesdex --headless -> real turn OK.

src/features/agent/application/turn_service.test.ts

@@ -0,0 +1,59 @@
+import { describe, expect, it } from "bun:test";
+import {
+  adaptiveMaxTokens,
+  conversationChars,
+  ErrorTracker,
+  truncateToolOutput,
+} from "./turn_service.ts";
+import { type ChatMessage, newConversation, systemMessage, userMessage, toolResultMessage } from "@zesdex/domain";
+
+describe("truncateToolOutput", () => {
+  it("short output is unchanged", () => {
+    expect(truncateToolOutput("short")).toBe("short");
+  });
+
+  it("long output preserves head and marks cut", () => {
+    const long = "x".repeat(12_000 + 500);
+    const truncated = truncateToolOutput(long);
+    expect(truncated.length).toBeLessThan(long.length);
+    expect(truncated).toContain("...[truncated");
+    expect(truncated.startsWith("xxx")).toBe(true);
+  });
+});
+
+describe("adaptiveMaxTokens", () => {
+  it("scales with request length", () => {
+    expect(adaptiveMaxTokens(10)).toBe(800);
+    expect(adaptiveMaxTokens(200)).toBe(1600);
+    expect(adaptiveMaxTokens(5000)).toBe(4096);
+  });
+});
+
+describe("ErrorTracker", () => {
+  it("injects recovery note after repeated errors", () => {
+    const tracker = new ErrorTracker();
+    const messages: ChatMessage[] = [];
+    tracker.record("read", "Error: File not found", messages);
+    tracker.record("read", "Error: File not found", messages);
+    expect(tracker.shouldStop()).toBe(false);
+    tracker.record("read", "Error: File not found", messages);
+    expect(messages.some((m) => m.content?.includes("[System note]"))).toBe(true);
+  });
+
+  it("stops after too many errors", () => {
+    const tracker = new ErrorTracker();
+    const messages: ChatMessage[] = [];
+    for (let i = 0; i < 8; i++) {
+      tracker.record("bash", `Error: boom ${i}`, messages);
+    }
+    expect(tracker.shouldStop()).toBe(true);
+  });
+});
+
+describe("conversationChars", () => {
+  it("sums content only", () => {
+    const conv = newConversation("sys", "s1");
+    conv.messages.push(systemMessage("sys"), userMessage("hello world"), toolResultMessage("id", "output"));
+    expect(conversationChars(conv.messages)).toBe(3 + 11 + 6);
+  });
+});