feat(HAI-090): remove package.json dependency from compiled binary

- Inline version/name resolution in bin.ts so the binary works without package.json
- Simplify build.ts by removing package.json bundling steps
- Remove unused dynamic package.json lookups in engine merger, triage, and executor
- Expand build-exe tests to verify binary runs independently of package.json
- Clean up obsolete engine unit tests tied to removed package.json logic

packages/cli/src/bin.ts

@@ -1,7 +1,45 @@
 #!/usr/bin/env node
 
-import { runDashboard } from "./commands/dashboard.js";
-import { runTaskCreate, runTaskList, runTaskMove, runTaskMerge, runTaskUpdate, runTaskLog, runTaskShow, runTaskAttach } from "./commands/task.js";
+/**
+ * Bootstrap: when running as a bun-compiled binary, the bundled pi-coding-agent
+ * reads package.json from the executable's directory at module-init time
+ * (top-level `readFileSync` in its config module). We redirect that read to a
+ * temp directory containing a minimal package.json so the binary works
+ * standalone without any co-located package.json.
+ *
+ * Node built-ins are safe to import statically — they have no side-effects
+ * that depend on package.json. All application imports MUST be dynamic
+ * (after the env is configured) so they resolve after PI_PACKAGE_DIR is set.
+ */
+import { mkdtempSync, writeFileSync, existsSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { tmpdir } from "node:os";
+
+// @ts-expect-error -- Bun-only global; undefined in Node
+const isBunBinary = typeof Bun !== "undefined" && !!Bun.embeddedFiles;
+
+if (isBunBinary) {
+  const execDir = dirname(process.execPath);
+  const localPkg = join(execDir, "package.json");
+
+  if (!existsSync(localPkg)) {
+    // Write a minimal package.json to a temp dir and redirect PI_PACKAGE_DIR
+    const tmp = mkdtempSync(join(tmpdir(), "hai-pkg-"));
+    writeFileSync(
+      join(tmp, "package.json"),
+      JSON.stringify(
+        { name: "hai", version: "0.1.0", type: "module", piConfig: { name: "hai", configDir: ".hai" } },
+        null,
+        2,
+      ) + "\n",
+    );
+    process.env.PI_PACKAGE_DIR = tmp;
+  }
+}
+
+// Dynamic imports so the pi-coding-agent config module sees PI_PACKAGE_DIR
+const { runDashboard } = await import("./commands/dashboard.js");
+const { runTaskCreate, runTaskList, runTaskMove, runTaskMerge, runTaskUpdate, runTaskLog, runTaskShow, runTaskAttach } = await import("./commands/task.js");
 
 const HELP = `
 hai — AI-orchestrated task board