feat: add manual export provider and ReviewRequest pattern

Implement Task 8.0 — Manual Export Provider with full provider abstraction:

Source files:
- src/providers/manual-export.js (104 lines) — new provider that wraps
  pre-built prompts in copy-ready format for ChatGPT Web/Business use
- src/providers/factory.js — register 'manual' provider in whitelist
- src/providers/openai.js — update JSDoc for ProviderRequest parameter

All 5 handlers updated with ReviewRequest pattern:
- src/tools/ask-chatgpt.js
- src/tools/debug-issue.js
- src/tools/review-code.js
- src/tools/review-plan.js
- src/tools/architecture-review.js
Each handler now packages shared data as { prompt, input } between step 5
and 6 of the orchestration flow.

Tests:
- test/providers/manual-export.test.js (56 tests) — covers structure,
  copy-ready box formatting, tool name detection, long prompts, Unicode,
  edge cases, provider contract compliance, idempotency
- test/providers/factory.test.js (+9 tests) — manual provider whitelist,
  factory routing, send delegation

Docs:
- ARCHITECTURE.md — provider selection table with openai/manual values
- README.md — provider comparison table and manual workflow description

test/providers/factory.test.js

@@ -1,5 +1,6 @@
 import { describe, it, expect, vi } from "vitest";
 import { createChatProvider, openaiProvider } from "../../src/providers/factory.js";
+import { manualExportProvider } from "../../src/providers/manual-export.js";
 
 function mockConfig(provider) {
   const cfg = { chatgptMcpProvider: provider };
@@ -195,3 +196,66 @@ describe("repeatability", () => {
     expect(p1).toBe(p2);
   });
 });
+
+// --- Manual provider ---
+
+describe("manual provider", () => {
+  it("supports manual provider via createChatProvider", () => {
+    const provider = createChatProvider({ chatgptMcpProvider: "manual" });
+    expect(provider.send).toBeDefined();
+  });
+
+  it("returns the same singleton instance for repeated calls with 'manual'", () => {
+    const p1 = createChatProvider({ chatgptMcpProvider: "manual" });
+    const p2 = createChatProvider({ chatgptMcpProvider: "manual" });
+    expect(p1).toBe(p2);
+  });
+
+  it("is different from openai provider", () => {
+    const manualP = createChatProvider({ chatgptMcpProvider: "manual" });
+    expect(manualP).not.toBe(openaiProvider);
+  });
+
+  it("can detect manual as a supported provider (not throw)", () => {
+    const provider = createChatProvider({ chatgptMcpProvider: "manual" });
+    expect(provider.send).toBeDefined();
+  });
+
+  it("manual provider send returns { content: string } shape", async () => {
+    const provider = createChatProvider({ chatgptMcpProvider: "manual" });
+    const result = await provider.send(
+      { prompt: "test prompt from manual env", input: { question: "hi" } },
+      {},
+    );
+    expect(result).toHaveProperty("content");
+    expect(typeof result.content).toBe("string");
+  });
+
+  it("manual provider output contains MANUAL EXPORT marker", async () => {
+    const provider = createChatProvider({ chatgptMcpProvider: "manual" });
+    const result = await provider.send({ prompt: "test", input: {} }, {});
+    expect(result.content).toContain("MANUAL EXPORT");
+  });
+
+  it("manual provider output contains COPY box delimiters", async () => {
+    const provider = createChatProvider({ chatgptMcpProvider: "manual" });
+    const result = await provider.send({ prompt: "test", input: {} }, {});
+    expect(result.content).toContain("┌");
+    expect(result.content).toContain("┐");
+    expect(result.content).toContain("┘");
+  });
+
+  it("can be switched from openai to manual and back", () => {
+    const p1 = createChatProvider({ chatgptMcpProvider: "openai" });
+    const p2 = createChatProvider({ chatgptMcpProvider: "manual" });
+    const p3 = createChatProvider({ chatgptMcpProvider: "openai" });
+    expect(p1).toBe(openaiProvider);
+    expect(p2).not.toBe(openaiProvider);
+    expect(p3).toBe(openaiProvider);
+  });
+
+  it("manual provider is not the same as openaiProvider singleton", () => {
+    const manualP = createChatProvider({ chatgptMcpProvider: "manual" });
+    expect(manualExportProvider).toBe(manualP);
+  });
+});