fix(tool): stop the socket gate rejecting every tool call on Windows

The tool gate ran access() on DAEMON_SOCKET_PATH, which on Windows is the named
pipe \\.\pipe\pi-browser-daemon. Named pipes are not filesystem entries, so
access() always fails there and every browser_* call returned "Browser harness
not initialized" no matter how healthy the daemon was. spawn.ts already skipped
the identical check for this reason; that knowledge is now one shared
daemonSocketMayExist() used by both call sites, with platform and path as
parameters so the branch is testable off-platform.

Report: docs/superpowers/reports/2026-07-26-bug-audit.md#f1

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/src/util/tool.ts b/src/util/tool.ts
index e4bb5ba..76087bc 100644
--- a/src/util/tool.ts
+++ b/src/util/tool.ts
@@ -8,8 +8,7 @@ import type {
   ToolRenderResultOptions,
 } from "@mariozechner/pi-coding-agent";
 import type { Component } from "@mariozechner/pi-tui";
-import { access } from "node:fs/promises";
-import { DAEMON_SOCKET_PATH } from "../daemon/protocol";
+import { daemonSocketMayExist } from "../daemon/spawn";
 import type { BrowserClient } from "../client";
 import type { Result } from "./result";
 
@@ -141,9 +140,7 @@ export const registerBrowserTool = (
         // Check daemon socket exists before attempting browser control.
         // If missing, the user hasn't run /browser-setup yet. Return a clear
         // error so the agent knows to direct the user to initialize.
-        try {
-          await access(DAEMON_SOCKET_PATH);
-        } catch {
+        if (!(await daemonSocketMayExist())) {
           return toToolResult(
             {
               success: false,