windows: the installed axiomcode command fails in PowerShell and cmd ("bash.exe" is not recognized), because npm's shim runs bash from PATH #1229

diff --git a/.gitignore b/.gitignore
index d53e24ef..f70e4558 100644
--- a/.gitignore
+++ b/.gitignore
@@ -129,6 +129,9 @@ oracles/
 # four binaries into the tree.
 [Oo]bj/
 [Bb]in/
+# ...except the repository's own bin/, which is the CLI and not build output: without this
+# every new file there, bin/axiomcode.js included, is silently left out of a commit.
+!/bin/
 *.user
 
 reports/
diff --git a/graph/test/tools/package-contents-test.sh b/graph/test/tools/package-contents-test.sh
index 68f18ac7..2937fa3e 100755
--- a/graph/test/tools/package-contents-test.sh
+++ b/graph/test/tools/package-contents-test.sh
@@ -56,12 +56,13 @@ try{
 let files;
 try{
   files=JSON.parse(execFileSync("npm",["pack","--dry-run","--json","--ignore-scripts"],
-    {cwd:root, encoding:"utf8", stdio:["ignore","pipe","ignore"], maxBuffer:64*1024*1024}))[0].files.map(f=>f.path);
+    {cwd:root, encoding:"utf8", stdio:["ignore","pipe","ignore"], maxBuffer:64*1024*1024, shell:process.platform==="win32"}))[0].files.map(f=>f.path);
 }catch(e){ console.log("  FAIL  npm pack --dry-run failed: "+e.message.split("\n")[0]); process.exit(1); }
 const has=(p)=>files.includes(p);
 const count=(re)=>files.filter(f=>re.test(f)).length;
 
 has("bin/axiomcode") ? ok("ships bin/axiomcode") : bad("does NOT ship bin/axiomcode");
+has("bin/axiomcode.js") ? ok("ships bin/axiomcode.js") : bad("does NOT ship bin/axiomcode.js, the command npm links");
 // The corpora are the bulk of the repository and run nothing for a consumer.
 count(/^graph\/test\//)===0 ? ok("does not ship graph/test") : bad("ships "+count(/^graph\/test\//)+" files under graph/test");
 count(/^parser\/src\/test-data\//)===0 ? ok("does not ship parser test-data") : bad("ships "+count(/^parser\/src\/test-data\//)+" files under parser/src/test-data");
diff --git a/package.json b/package.json
index bfb73b7a..0d59e6d3 100644
--- a/package.json
+++ b/package.json
@@ -36,7 +36,7 @@
     "@axiomcode/engine-win32-x64": "0.1.0"
   },
   "bin": {
-    "axiomcode": "bin/axiomcode"
+    "axiomcode": "bin/axiomcode.js"
   },
   "files": [
     "bin/",
diff --git a/bin/axiomcode.js b/bin/axiomcode.js
new file mode 100644
index 00000000..2ebd2358
--- /dev/null
+++ b/bin/axiomcode.js
@@ -0,0 +1,65 @@
+#!/usr/bin/env node
+// ─────────────────────────────────────────────────────────────────────────────
+// The installed `axiomcode` command. It only finds a bash and hands everything to
+// bin/axiomcode, which is the CLI.
+//
+// WHY A NODE LAUNCHER. npm writes the command's wrappers itself from the `bin` entry: a
+// symlink on POSIX, and on Windows an axiomcode.cmd and an axiomcode.ps1 that run whatever
+// the script's shebang names. For bin/axiomcode that is `bash`, so both wrappers run a bare
+// `bash.exe` from PATH -- and a default Git for Windows install puts Git\cmd on PATH, not
+// Git\bin, so PowerShell and cmd fail with "'bash.exe' is not recognized". Adding Git\bin to
+// PATH is not a fix either: once WSL is installed, C:\Windows\System32\bash.exe comes first on
+// the machine PATH, and it is WSL's bash, which runs this Windows install inside Linux where
+// neither the Windows node nor a C:/ path exists. A Node shebang makes npm's wrappers run
+// node, which is always there, and the choice of bash is made here instead of by PATH.
+//
+// On Windows, in order: $AXIOMCODE_BASH, Git's own bash located from `git --exec-path`, then
+// the default install locations. PATH is never searched for bash, so WSL's is never taken.
+// Everywhere else it is plain `bash`, as the shebang of bin/axiomcode already assumes.
+// ─────────────────────────────────────────────────────────────────────────────
+'use strict';
+const { spawnSync, execFileSync } = require('child_process');
+const fs = require('fs');
+const path = require('path');
+
+const script = path.join(__dirname, 'axiomcode');
+
+function gitBash() {
+  const candidates = [];
+  try {
+    // <git>/mingw64/libexec/git-core, or <git>/libexec/git-core on some layouts. Git\bin\bash.exe
+    // is the wrapper that puts mingw64/bin and usr/bin on PATH, which the pipeline needs;
+    // usr\bin\bash.exe alone does not.
+    const exec = execFileSync('git', ['--exec-path'], { encoding: 'utf8', stdio: ['ignore', 'pipe', 'ignore'], windowsHide: true }).trim();
+    for (let d = path.resolve(exec), i = 0; i < 4; i++, d = path.dirname(d)) candidates.push(path.join(d, 'bin', 'bash.exe'));
+  } catch { /* no git on PATH: fall through to the default locations */ }
+  for (const base of [process.env.ProgramFiles, process.env['ProgramFiles(x86)'], process.env.LOCALAPPDATA && path.join(process.env.LOCALAPPDATA, 'Programs')]) {
+    if (base) candidates.push(path.join(base, 'Git', 'bin', 'bash.exe'));
+  }
+  return candidates.find((p) => fs.existsSync(p));
+}
+
+function resolveBash() {
+  const override = process.env.AXIOMCODE_BASH;
+  if (override) {
+    if (fs.existsSync(override)) return override;
+    fail(`AXIOMCODE_BASH is set to ${override}, which does not exist.`);
+  }
+  if (process.platform !== 'win32') return 'bash';
+  const found = gitBash();
+  if (found) return found;
+  fail('axiomcode needs the bash that comes with Git for Windows, and none was found.\n' +
+       '   • install Git for Windows (https://git-scm.com/download/win), or\n' +
+       '   • set AXIOMCODE_BASH to the full path of a Git Bash bash.exe (not C:\Windows\System32\bash.exe, which is WSL).');
+}
+
+function fail(msg) {
+  process.stderr.write(`❌ ${msg}\n`);
+  process.exit(127);
+}
+
+const r = spawnSync(resolveBash(), [script, ...process.argv.slice(2)], { stdio: 'inherit', windowsHide: false });
+if (r.error) fail(`could not start bash: ${r.error.message}`);
+// Die of the same signal the CLI died of, so a caller sees what really happened.
+if (r.signal) process.kill(process.pid, r.signal);
+process.exit(r.status ?? 1);