Implement all stubs: parsePackageMap, LLM heuristics, tree-sitter AST, patch rewrite, reinit

- format.ts: Full parsePackageMap implementation with round-trip support
- llm-extract.ts: Heuristic-based extraction without LLM API (regex exports,
  imports, purpose inference from filename patterns)
- ast-extract.ts: Tree-sitter integration for TypeScript/TSX with fallback
  for other languages
- init.ts: Refactored to expose generateDirectoryMap helper, reinitPath
  delegates to initProject
- patch.ts: Small packages now use generateDirectoryMap for full rewrite
- discover.ts: Cleaned up require('fs') to use proper ES import
- Tests: 8 tests covering format round-trip and LLM heuristics
- All TypeScript compiles clean, all tests pass

tests/llm-extract.test.ts

@@ -0,0 +1,63 @@
+import { describe, it, expect } from "vitest";
+import { extractFileLLM } from "../src/llm-extract.js";
+import { writeFileSync, mkdtempSync } from "fs";
+import { join } from "path";
+import { tmpdir } from "os";
+
+describe("llm-extract heuristics", () => {
+	it("extracts TypeScript exports", async () => {
+		const dir = mkdtempSync(join(tmpdir(), "pi-map-"));
+		const file = join(dir, "test.ts");
+		writeFileSync(
+			file,
+			`export function foo() {}
+export class Bar {}
+export const baz = 1;
+export type Qux = string;
+export { a, b as c };
+`,
+		);
+		const result = await extractFileLLM(file);
+		expect(result.exports).toContain("foo");
+		expect(result.exports).toContain("Bar");
+		expect(result.exports).toContain("baz");
+		expect(result.exports).toContain("Qux");
+		expect(result.exports).toContain("a");
+		expect(result.exports).toContain("b");
+	});
+
+	it("extracts TypeScript imports", async () => {
+		const dir = mkdtempSync(join(tmpdir(), "pi-map-"));
+		const file = join(dir, "test.ts");
+		writeFileSync(
+			file,
+			`import { foo } from "./bar";
+import * as baz from "baz-lib";
+import type { Qux } from "qux";
+const x = require("legacy");
+`,
+		);
+		const result = await extractFileLLM(file);
+		expect(result.deps).toContain("./bar");
+		expect(result.deps).toContain("baz-lib");
+		expect(result.deps).toContain("qux");
+		expect(result.deps).toContain("legacy");
+	});
+
+	it("infers purpose from filename patterns", async () => {
+		const dir = mkdtempSync(join(tmpdir(), "pi-map-"));
+		const file = join(dir, "userController.ts");
+		writeFileSync(file, `export class UserController {}`);
+		const result = await extractFileLLM(file);
+		expect(result.purpose).toMatch(/Controller|Exports/);
+	});
+
+	it("handles non-code files", async () => {
+		const dir = mkdtempSync(join(tmpdir(), "pi-map-"));
+		const file = join(dir, "Dockerfile");
+		writeFileSync(file, `FROM node:20\nWORKDIR /app`);
+		const result = await extractFileLLM(file);
+		expect(result.purpose).toBe("Container definition");
+		expect(result.exports).toEqual([]);
+	});
+});