chore: migrate from bun to pnpm + vitest + esbuild

- Replace bun:test with vitest across all packages
- Replace bun build with esbuild
- Replace bun:sqlite with better-sqlite3
- Fix OCAS Store API: store.put/get → store.cas.put/get
- Fix vitest vi.mock hoisting (vi.hoisted)
- Add pnpm-workspace.yaml and pnpm-lock.yaml
- Update all package.json test/build scripts

WIP: 8 failures remain in agent-hermes (bun engines check + sqlite migration)

Refs #26

packages/agent-hermes/__tests__/acp-client.test.ts

@@ -1,5 +1,4 @@
-import { afterEach, beforeEach, describe, expect, it } from "bun:test";
-
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
 import { HermesAcpClient } from "../src/acp-client.js";
 
 describe("handleSessionUpdate — text extraction", () => {

packages/agent-hermes/__tests__/hermes-prompt.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, test } from "bun:test";
+import { describe, expect, test } from 'vitest';
 import type { ThreadId } from "@united-workforce/protocol";
 import type { AgentContext } from "@united-workforce/util-agent";
 import { buildHermesPrompt } from "../src/hermes.js";

packages/agent-hermes/__tests__/integration/acp-client.integration.test.ts

@@ -1,5 +1,4 @@
-import { afterEach, beforeEach, describe, expect, it } from "bun:test";
-
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
 import { HermesAcpClient } from "../../src/acp-client.js";
 
 const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;

packages/agent-hermes/__tests__/integration/resume-e2e.integration.test.ts

@@ -1,5 +1,4 @@
-import { afterEach, describe, expect, it } from "bun:test";
-
+import { afterEach, describe, expect, it } from 'vitest';
 import { HermesAcpClient } from "../../src/acp-client.js";
 
 /**

packages/agent-hermes/__tests__/issue-551.test.ts

@@ -1,8 +1,10 @@
-import { describe, expect, test } from "bun:test";
+import { describe, expect, test } from 'vitest';
+import { dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
 import { readFileSync } from "node:fs";
 import { join } from "node:path";
 
-const PKG_ROOT = join(import.meta.dir, "..");
+const PKG_ROOT = join(dirname(fileURLToPath(import.meta.url)), "..");
 
 describe("Issue #551 — bin entry & engines", () => {
   test("package.json declares bun in engines", () => {

packages/agent-hermes/__tests__/session-detail.test.ts

@@ -1,5 +1,5 @@
-import { Database } from "bun:sqlite";
-import { describe, expect, test } from "bun:test";
+import Database from "better-sqlite3";
+import { describe, expect, test } from 'vitest';
 import { mkdtemp, rm, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
@@ -106,7 +106,7 @@ describe("storeHermesSessionDetail", () => {
 
     expect(output).toBe("done");
 
-    const detailNode = store.get(detailHash);
+    const detailNode = store.cas.get(detailHash);
     expect(detailNode).not.toBeNull();
     if (detailNode === null) {
       return;