fix(hooks): shared spawn-bin helper — all three AskUserQuestion hooks were inert on Windows

The plan-tune hooks resolved bin scripts via new URL(import.meta.url).pathname
(which doubles the drive letter on Windows: /C:/C:/...) and spawnSync'd
extensionless bash scripts directly (unrunnable without a shell association)
— so question logging, preferences, and the error fallback all silently
no-op'd on Windows, and /plan-tune collected no data. A single spawn-bin.ts
helper now owns bin resolution (fileURLToPath) and win32 bash routing for
every hook, with static tripwires so a future hook can't reintroduce the
raw pattern. This is the one Windows-spawn idiom for hook code.

Fixes #2356.

Contributed by @rafassousa (PR #2504; supersedes PR #2399 by @chuchu2781).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

hosts/claude/hooks/spawn-bin.ts

@@ -0,0 +1,43 @@
+/**
+ * Windows-safe resolution + spawn for gstack's bash bins. Two Windows-only
+ * bugs made every hook subprocess a silent no-op; both are fixed here so all
+ * call sites are covered at once.
+ *
+ * 1. `new URL(import.meta.url).pathname` yields `/C:/Users/...`; path.resolve
+ *    then rebases it onto the drive root as `C:\C:\Users\...`. fileURLToPath
+ *    is the correct conversion. (ENOENT before the bin ever ran.)
+ * 2. `bin/gstack-*` are extensionless bash scripts. Windows has no shebang
+ *    support, so they must be handed to bash explicitly.
+ */
+import * as fs from 'fs';
+import * as path from 'path';
+import { fileURLToPath } from 'url';
+import { spawnSync, type SpawnSyncOptions } from 'child_process';
+
+// Forward slashes on purpose: Bun's spawnSync on Windows returns ENOENT for a
+// backslash exe path containing spaces.
+const GIT_BASH = 'C:/Program Files/Git/bin/bash.exe';
+
+/** bash Windows itself can execute — env override, Git Bash, then PATH. */
+function bashExe(): string {
+  return process.env.GSTACK_BASH || (fs.existsSync(GIT_BASH) ? GIT_BASH : 'bash');
+}
+
+/** gstack install root. This file lives at hosts/claude/hooks/. */
+export function repoRoot(): string {
+  const here = path.dirname(fileURLToPath(import.meta.url));
+  return path.resolve(here, '..', '..', '..');
+}
+
+/** Absolute path to a `bin/` script. */
+export function binPath(name: string): string {
+  return path.join(repoRoot(), 'bin', name);
+}
+
+/** Resolve `name` under bin/ and run it, via bash on Windows. */
+export function runBin(name: string, args: string[], opts: SpawnSyncOptions) {
+  const bin = binPath(name);
+  return process.platform === 'win32'
+    ? spawnSync(bashExe(), [bin, ...args], opts)
+    : spawnSync(bin, args, opts);
+}