fix: invoke zeroshot via node on Windows

[haosenwang1018]

Summary

• add a small buildZeroshotSpawnSpec() helper for self-invocation
• on Windows, spawn process.execPath with cli/index.js instead of trying to execute bare zeroshot
• reuse that helper in both agent-task-executor and claude-task-runner
• add regression coverage for the Windows vs non-Windows spawn spec

Why

Issue #457 reports that spawn('zeroshot', ...) fails on Windows because npm global commands are exposed as .cmd wrappers, which Node cannot execute the same way as Unix binaries.

This PR fixes the smallest high-impact part first: zeroshot spawning itself. On Windows it now invokes Node directly with the CLI script path, avoiding the .cmd wrapper and the resulting ENOENT failures.

Testing

• ./node_modules/.bin/mocha tests/providers/detection.test.js

Part of #457

[tomdps]

Status review (2026-07-29):

• Windows-support theme: yes—this is the self-invocation slice of Windows compatibility: npm global commands cannot be spawned without shell workaround #457/[BUG] Error: spawn zeroshot ENOENT #57, alongside the provider-wrapper, console-window, and IPC work in fix: resolve npm CLI wrappers in Windows watchers #475/fix: hide child process windows on Windows #472/[BUG] Windows Native Version Not Working #63. Native Windows is currently stopped earlier by runPreflight(), so this defect is latent rather than a supported current path; the underlying direct spawns remain on main.
• Not merge-ready: GitHub reports merge conflicts (mergeable=false, mergeable_state=dirty) and no check runs/status contexts; the provider-detection and windowsHide changes are already present on main.
• Rework against current main and use one Windows-safe command/args spec for every direct host task-CLI call: the initial task run; launch cancellation/failure cleanup in createPendingTaskLaunchHandle() and cleanupPersistedTaskAfterLaunchFailure(); both waitForTaskReady variants; _followLogs; createLogFollower; killTask; and hook-failure log retrieval in agent-hook-executor (status, get-log-path, kill, and logs). The detached CLI re-exec already uses process.execPath; provider .cmd execution in task-lib/watcher.js remains the broader Windows compatibility: npm global commands cannot be spawned without shell workaround #457/fix: resolve npm CLI wrappers in Windows watchers #475 slice.