fix(daemon): prefer active CLI for launchd (#67)

## Summary
- prefer the resolved active Hack CLI when writing or repairing the
launchd service
- retain the global Hack binary as a fallback when no active executable
is available
- cover mixed Homebrew plus stale local-development shim installs

## Verification
- bun test tests/launchd.test.ts
- bun run check
- bun run typecheck
- bun run build
- bun test: 907 pass, 5 skip; one process-table test sandbox-blocked
- bun test tests/daemon-command.test.ts outside the restricted process
sandbox: 1 pass

Author: roodboi

src/daemon/launchd.ts

@@ -161,30 +161,38 @@ export async function installLaunchdService({
  * launchd should execute `hack` directly; writing `bun` here can break daemon
  * startup when Bun is unavailable in non-interactive PATH contexts.
  */
-async function resolveLaunchdHackBinPath(opts: {
+export async function resolveLaunchdHackBinPath(opts: {
   readonly invocation: {
     readonly bin: string;
     readonly args: readonly string[];
   };
+  readonly findExecutable?: typeof findExecutableInPath;
+  readonly exists?: typeof pathExists;
+  readonly globalHackBinPath?: string;
+  readonly argvPath?: string | null;
 }): Promise<string | null> {
-  // Stable locations first: versioned paths (homebrew Cellar) rot on
-  // upgrade, and argv paths inside a compiled Bun binary report the
-  // virtual /$bunfs mount, which only exists inside that process —
-  // launchd exec'ing it fails forever with status 78.
+  const findExecutable = opts.findExecutable ?? findExecutableInPath;
+  const exists = opts.exists ?? pathExists;
+
+  // Prefer the executable selected for this invocation. A valid
+  // ~/.hack/bin/hack may be an older local-development shim alongside a
+  // newer Homebrew install; choosing that fallback first makes every daemon
+  // restart downgrade hackd. Keep stable PATH/invocation locations ahead of
+  // the global fallback, while still rejecting compiled Bun virtual paths.
   const candidates = [
-    resolve(resolveGlobalHackDir(), "bin", "hack"),
-    await findExecutableInPath("hack"),
     opts.invocation.args[0] ?? null,
     opts.invocation.bin,
-    process.argv[1] ?? null,
+    await findExecutable("hack"),
+    opts.globalHackBinPath ?? resolve(resolveGlobalHackDir(), "bin", "hack"),
+    opts.argvPath === undefined ? (process.argv[1] ?? null) : opts.argvPath,
   ];
 
   for (const raw of candidates) {
     const path = normalizeHackExecutablePath(raw);
     if (!path) {
       continue;
     }
-    if (await pathExists(path)) {
+    if (await exists(path)) {
       return path;
     }
   }

tests/launchd.test.ts

@@ -1,6 +1,9 @@
 import { describe, expect, test } from "bun:test";
 import { DAEMON_LAUNCHD_LABEL } from "../src/constants.ts";
-import { renderLaunchdPlist } from "../src/daemon/launchd.ts";
+import {
+  renderLaunchdPlist,
+  resolveLaunchdHackBinPath,
+} from "../src/daemon/launchd.ts";
 
 describe("launchd plist generation", () => {
   test("renders plist with RunAtLoad false", () => {
@@ -118,3 +121,31 @@ describe("daemon constants", () => {
     expect(DAEMON_LAUNCHD_LABEL).toMatch(/^[a-z]+\.[a-z]+\.[a-z]+$/);
   });
 });
+
+describe("launchd executable resolution", () => {
+  test("prefers the active CLI over an older global development shim", async () => {
+    const resolved = await resolveLaunchdHackBinPath({
+      invocation: { bin: "/opt/homebrew/bin/hack", args: [] },
+      findExecutable: () => "/opt/homebrew/bin/hack",
+      exists: async (path) =>
+        path === "/opt/homebrew/bin/hack" ||
+        path === "/Users/testuser/.hack/bin/hack",
+      globalHackBinPath: "/Users/testuser/.hack/bin/hack",
+      argvPath: null,
+    });
+
+    expect(resolved).toBe("/opt/homebrew/bin/hack");
+  });
+
+  test("retains the global binary as a fallback", async () => {
+    const resolved = await resolveLaunchdHackBinPath({
+      invocation: { bin: "bun", args: ["/$bunfs/root/hack"] },
+      findExecutable: () => null,
+      exists: async (path) => path === "/Users/testuser/.hack/bin/hack",
+      globalHackBinPath: "/Users/testuser/.hack/bin/hack",
+      argvPath: "/$bunfs/root/hack",
+    });
+
+    expect(resolved).toBe("/Users/testuser/.hack/bin/hack");
+  });
+});