feat: move LLM cache to project-local directory

- Cache now lives in <project>/.pi-project-map/cache/llm-cache.json
- Removed global ~/.cache/pi-project-map/ usage
- Cache travels with the project, no cross-project collisions
- Easy to invalidate: rm -rf .pi-project-map/cache/

Files changed:
- llm-cache.ts: accept cacheDir parameter, default to project-local
- llm-extract.ts: pass cacheDir through to cache functions
- init.ts: pass rootPath as cacheDir
- patch.ts: accept and pass cacheDir
- cli.ts: pass targetPath as cacheDir
- pi-extension.ts: pass ctx.cwd as cacheDir
- Tests updated to use temp dirs for cache isolation

tests/llm-cache.test.ts

@@ -1,10 +1,10 @@
 import { describe, it, expect, beforeEach, afterEach } from "vitest";
 import { getCached, setCached } from "../src/llm-cache.js";
-import { existsSync, unlinkSync, rmdirSync } from "fs";
+import { existsSync, unlinkSync } from "fs";
 import { join } from "path";
-import { homedir } from "os";
+import { tmpdir } from "os";
 
-const TEST_CACHE_DIR = join(homedir(), ".cache", "pi-project-map");
+const TEST_CACHE_DIR = join(tmpdir(), "pi-project-map-test-cache");
 const TEST_CACHE_FILE = join(TEST_CACHE_DIR, "llm-cache.json");
 
 describe("llm-cache", () => {
@@ -21,20 +21,20 @@ describe("llm-cache", () => {
 	});
 
 	it("returns undefined for missing entries", () => {
-		const result = getCached("nonexistent-hash");
+		const result = getCached("nonexistent-hash", TEST_CACHE_DIR);
 		expect(result).toBeUndefined();
 	});
 
 	it("stores and retrieves cached results", () => {
-		setCached("abc123", "PURPOSE: test\nDEPS: none\nCONCEPTS: none");
-		const result = getCached("abc123");
+		setCached("abc123", "PURPOSE: test\nDEPS: none\nCONCEPTS: none", TEST_CACHE_DIR);
+		const result = getCached("abc123", TEST_CACHE_DIR);
 		expect(result).toBe("PURPOSE: test\nDEPS: none\nCONCEPTS: none");
 	});
 
 	it("overwrites existing entries", () => {
-		setCached("abc123", "old");
-		setCached("abc123", "new");
-		const result = getCached("abc123");
+		setCached("abc123", "old", TEST_CACHE_DIR);
+		setCached("abc123", "new", TEST_CACHE_DIR);
+		const result = getCached("abc123", TEST_CACHE_DIR);
 		expect(result).toBe("new");
 	});
 });

tests/llm-extract.test.ts

@@ -75,7 +75,7 @@ describe("llm-extract with mock client", () => {
 			},
 		};
 
-		const result = await extractFileLLM(file, mockClient);
+		const result = await extractFileLLM(file, mockClient, tmpdir());
 		expect(result.purpose).toBe("Test file");
 		expect(result.deps).toEqual([]);
 		expect(result.concepts).toContain("testing");

tests/llm-integration.test.ts

@@ -55,7 +55,7 @@ describe.skipIf(!hasKimiKey)("LLM integration with Kimi", () => {
 		);
 
 		const client = createLLMClient("kimi", { model: kimiModel });
-		const result = await extractFileLLM(file, client);
+		const result = await extractFileLLM(file, client, dir);
 
 		expect(result.purpose).toBeTruthy();
 		expect(result.purpose.length).toBeGreaterThan(5);
@@ -90,12 +90,12 @@ describe.skipIf(!hasKimiKey)("LLM integration with Kimi", () => {
 		writeFileSync(file, `export const version = "1.0.0";`);
 
 		const client = createLLMClient("kimi", { model: kimiModel });
-		const result1 = await extractFileLLM(file, client);
+		const result1 = await extractFileLLM(file, client, dir);
 		expect(result1.purpose).toBeTruthy();
 
 		// Second call should hit cache — much faster
 		const start = Date.now();
-		const result2 = await extractFileLLM(file, client);
+		const result2 = await extractFileLLM(file, client, dir);
 		const elapsed = Date.now() - start;
 
 		expect(result2.purpose).toBe(result1.purpose);
@@ -119,7 +119,7 @@ describe.skipIf(!hasKimiKey)("LLM integration with Kimi", () => {
 		const start = Date.now();
 		const results = await processFiles(
 			files,
-			async (f) => extractFileLLM(f, client),
+			async (f) => extractFileLLM(f, client, dir),
 			{ concurrency: 3, maxRetries: 1, retryDelaysMs: [2000] },
 		);
 		const elapsed = Date.now() - start;
@@ -145,7 +145,7 @@ describe.skipIf(!hasKimiKey)("LLM integration with Kimi", () => {
 			return originalComplete(...args);
 		};
 
-		const result = await extractFileLLM(file, trackingClient);
+		const result = await extractFileLLM(file, trackingClient, dir);
 		expect(result.purpose).toBe("Large/generated file");
 		expect(calls).toBe(0); // Should never call LLM for large files
 	});

tests/pi-extension.test.ts

@@ -19,13 +19,23 @@ vi.mock("typebox", () => ({
 vi.mock("@mariozechner/pi-ai", () => ({
 	complete: vi.fn(async (_model: any, _context: any) => ({
 		role: "assistant" as const,
-		content: [{ type: "text", text: "PURPOSE: Test file\nDEPS: none\nCONCEPTS: testing" }],
+		content: [
+			{
+				type: "text",
+				text: "PURPOSE: Test file\nDEPS: none\nCONCEPTS: testing",
+			},
+		],
 	})),
 }));
 
 import extension from "../pi-extension.js";
 
-const CACHE_FILE = join(homedir(), ".cache", "pi-project-map", "llm-cache.json");
+const CACHE_FILE = join(
+	homedir(),
+	".cache",
+	"pi-project-map",
+	"llm-cache.json",
+);
 function clearCache() {
 	if (existsSync(CACHE_FILE)) unlinkSync(CACHE_FILE);
 }
@@ -43,9 +53,16 @@ describe("pi-extension", () => {
 		mockNotify = vi.fn();
 		mockCtx = {
 			cwd: "/home/project",
-			model: { provider: "openai", id: "gpt-4o-mini", api: "openai-completions" },
+			model: {
+				provider: "openai",
+				id: "gpt-4o-mini",
+				api: "openai-completions",
+			},
 			modelRegistry: {
-				getApiKeyAndHeaders: vi.fn(async () => ({ apiKey: "test-key", headers: {} })),
+				getApiKeyAndHeaders: vi.fn(async () => ({
+					apiKey: "test-key",
+					headers: {},
+				})),
 			},
 			ui: { notify: mockNotify },
 		};