feat: M7 proper LLM integration with dual providers, caching, and parallel batching

- Add LLM client abstraction (src/llm-client.ts) with factory pattern
- Add OpenAI-compatible external client (src/external-llm-client.ts)
- Add Kimi.com client using Anthropic-based API (src/kimi-llm-client.ts)
- Add Pi native LLM stub (src/pi-llm-client.ts) for future ExtensionAPI wiring
- Add SHA-256 disk cache at ~/.cache/pi-project-map/ (src/llm-cache.ts)
- Add parallel batching with p-limit, retry + exponential backoff (src/llm-batch.ts)
- Rewrite llm-extract.ts to use real LLM calls with structured prompts
  - File-level: PURPOSE, DEPS, CONCEPTS
  - Package-level: ROLE, ARCH
  - Context truncation, 50KB skip, cache before LLM call
- Wire CLI with --llm-provider, --llm-model, --llm-base-url flags
- Update config.ts with llmProvider, llmBaseUrl fields
- Update init.ts and patch.ts to accept optional LLMClient
- Add sample project fixture for manual testing
- Add tests: llm-cache (3), llm-batch (5), llm-integration (8 with real Kimi API),
  pi-extension (14 mocked)
- All 56 tests pass

src/patch.ts

@@ -6,10 +6,14 @@ import { extractFileAST } from "./ast-extract.js";
 import { mergeFileData } from "./merge.js";
 import { generateDirectoryMap } from "./init.js";
 import { readdirSync, statSync } from "fs";
+import type { LLMClient } from "./llm-client.js";
 
 const SMALL_PACKAGE_THRESHOLD = 10;
 
-export async function patchFile(filePath: string): Promise<void> {
+export async function patchFile(
+	filePath: string,
+	llmClient?: LLMClient,
+): Promise<void> {
 	const dirPath = dirname(filePath);
 	const mapPath = join(dirPath, ".pi-map.md");
 
@@ -31,18 +35,21 @@ export async function patchFile(filePath: string): Promise<void> {
 			return st.isFile();
 		});
 		const relDir = relative(process.cwd(), dirPath) || ".";
-		await generateDirectoryMap({
-			dirPath,
-			relativePath: relDir,
-			files,
-		});
+		await generateDirectoryMap(
+			{
+				dirPath,
+				relativePath: relDir,
+				files,
+			},
+			llmClient,
+		);
 		console.log(
 			`Full rewrite of ${mapPath} (small package: ${allFiles.length} files)`,
 		);
 	} else {
 		// Section-level patch
 		const existing = parsePackageMap(readFileSync(mapPath, "utf8"));
-		const llmData = await extractFileLLM(filePath);
+		const llmData = await extractFileLLM(filePath, llmClient);
 		const astData = await extractFileAST(filePath);
 		const fileName = basename(filePath);
 		const updatedFile = mergeFileData(fileName, llmData, astData);