refactor(node): platform abstraction for Windows portability (W1-W2-W5-W6-W7)

Platform directories, signal handling, chmod guards, ffmpeg discovery,
and platform-conditional CLI messages — all testable on Linux.

See docs/WINDOWS-PORT.md §5 for the plan these implement.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 26 insertions, 10 deletions

diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index e071074..2a97246 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -43,6 +43,20 @@ app.commandLine.appendSwitch('class', 'MeshBay');
 const UI_DIR = path.join(__dirname, '..', 'ui');
 const SCHEME = 'app';
 
+// ── Platform directories ────────────────────────────────────────────────────
+
+function meshbayConfigDir() {
+  if (process.platform === 'win32')
+    return path.join(process.env.LOCALAPPDATA || os.homedir(), 'meshbay');
+  return path.join(os.homedir(), '.config', 'meshbay');
+}
+
+function meshbayDataDir() {
+  if (process.platform === 'win32')
+    return path.join(process.env.LOCALAPPDATA || os.homedir(), 'meshbay', 'data');
+  return path.join(os.homedir(), '.local', 'share', 'meshbay');
+}
+
 // The policy, sent as a header on every response.
 //
 // Not a <meta> tag: `frame-ancestors` is ignored there — Chromium says so in
@@ -697,13 +711,13 @@ function registerBridge() {
   let _nodePairingCode = null;
 
   function nodeConfigPath() {
-    return path.join(os.homedir(), '.config', 'meshbay', 'node.toml');
+    return path.join(meshbayConfigDir(), 'node.toml');
   }
 
   function readNodeConfig() {
     try {
       const text = fs.readFileSync(nodeConfigPath(), 'utf8');
-      let dataDir = path.join(os.homedir(), '.local', 'share', 'meshbay');
+      let dataDir = meshbayDataDir();
       let uiPort = 18000;
       const dataMatch = text.match(/^\s*data_dir\s*=\s*"([^"]+)"/m);
       if (dataMatch) {
@@ -750,11 +764,14 @@ function registerBridge() {
   });
 
   function findNodeBinary() {
-    const local = path.join(os.homedir(), '.local', 'bin', 'meshbay-node');
-    if (fs.existsSync(local)) return local;
+    if (process.platform !== 'win32') {
+      const local = path.join(os.homedir(), '.local', 'bin', 'meshbay-node');
+      if (fs.existsSync(local)) return local;
+    }
+    const cmd = process.platform === 'win32' ? 'where.exe' : 'which';
     return new Promise((resolve) => {
-      execFile('which', ['meshbay-node'], (err, stdout) => {
-        resolve(err ? null : stdout.trim());
+      execFile(cmd, ['meshbay-node'], (err, stdout) => {
+        resolve(err ? null : stdout.trim().split('\n')[0]);
       });
     });
   }
@@ -832,8 +849,7 @@ function registerBridge() {
 
   async function probeNode() {
     const nc = readNodeConfig();
-    const dataDir = nc ? nc.dataDir
-      : path.join(os.homedir(), '.local', 'share', 'meshbay');
+    const dataDir = nc ? nc.dataDir : meshbayDataDir();
     const port = nc ? nc.uiPort : 18000;
     const token = readNodeToken(dataDir);
     if (!token) return null;
@@ -852,8 +868,8 @@ function registerBridge() {
   }
 
   function provisionNode(hubUrl, username) {
-    const configDir = path.join(os.homedir(), '.config', 'meshbay');
-    const dataDir = path.join(os.homedir(), '.local', 'share', 'meshbay');
+    const configDir = meshbayConfigDir();
+    const dataDir = meshbayDataDir();
     fs.mkdirSync(configDir, { recursive: true });
     fs.mkdirSync(dataDir, { recursive: true });