feat: Windows installer (W4) — one per-user NSIS package, client + node

`npm run dist:win` produces MeshBay-Setup-<version>.exe: the Electron client
and, beside it under resources/node-runtime/, the frozen meshbay-node daemon
(meshbay-common inside it). No hub. Per-user, no elevation — matches the W3
constraint that a logon-triggered scheduled task needs admin.

electron-builder / package.json
  build.win   nsis, build/icon.ico, extraResources -> node-runtime/
  build.nsis  oneClick:false perMachine:false allowElevation:false
              allowToChangeInstallationDirectory:true
  dist:win    -> packaging/win/build-win.ps1 (mirrors dist -> build-client.sh)

packaging/win/
  meshbay-node.spec + node-entry.py   PyInstaller freeze of
      meshbay_node.daemon:main. The awkward deps (aiortc, av, aioquic,
      pydantic_core, uvicorn, watchdog, guessit, blake3, tzdata) are pulled
      in whole with collect_all — that list is expected to grow when a frozen
      run raises ModuleNotFoundError.
  build-node-runtime.ps1   throwaway venv -> pip install -> PyInstaller ->
      packages/meshbay-client/node-runtime/ (gitignored)
  build-win.ps1            Node>=22 check, npm ci, Electron bump, sync-ui,
      node runtime, electron-builder --win nsis
  bump-electron.mjs        the Chromium-CVE "build against latest Electron"
      policy, out of the PS script (5.1 here-string terminator rules)
  README.md

PyInstaller, not the python-embed zip: the frozen meshbay-node.exe is a
genuine relocatable single binary, which is what src/main.js:findNodeBinary
spawns (process.resourcesPath/node-runtime/meshbay-node.exe when packaged) and
what the W3 autostart launcher points at. The embeddable zip needs pip to make
that wrapper and the wrapper bakes in an absolute interpreter path.

build/installer.nsh: on uninstall, taskkill meshbay-node.exe and delete the W3
Startup .vbs (it would point wscript at a deleted binary every sign-in).
%LOCALAPPDATA%\meshbay\ — node.toml, keystore.enc — is never touched.

ffmpeg is not bundled by default (node finds it on PATH); build-win.ps1
-FfmpegDir copies ffmpeg.exe/ffprobe.exe in for a self-contained installer.

Verified on the Windows guest: PyInstaller freeze builds first try
(node-runtime 147 MB), frozen `meshbay-node status` talks to the live daemon's
loopback API; electron-builder --win nsis produces MeshBay-Setup-0.1.0.exe
(155 MB), oneClick/perMachine flags applied, node-runtime bundled at the path
findNodeBinary expects. test_packaging_win.py (14) pins the config invariants
and the NSIS <-> platform.py autostart seam. Node suite 798 pass / 34 skip.

Open: Authenticode signing (13.9 — unsigned => SmartScreen), Windows CI
(18.3), electron-updater. First clean-machine install + DPAPI + autostart
round-trip is a manual check.

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

4 files changed, 58 insertions, 3 deletions

diff --git a/packages/meshbay-client/build/icon.ico b/packages/meshbay-client/build/icon.ico
new file mode 100644
index 0000000..2766f24
--- /dev/null
+++ b/packages/meshbay-client/build/icon.ico
diff --git a/packages/meshbay-client/build/installer.nsh b/packages/meshbay-client/build/installer.nsh
new file mode 100644
index 0000000..cf8e5ff
--- /dev/null
+++ b/packages/meshbay-client/build/installer.nsh
@@ -0,0 +1,24 @@
+; electron-builder NSIS customisation (auto-included: build/installer.nsh).
+;
+; Per-user install, no elevation (package.json build.nsis). These macros only
+; deal with the one piece of state that lives outside the install directory:
+; the W3 "run at sign-in" launcher the node's own CLI can create.
+;
+; Deliberately NOT touched here:
+;   - %LOCALAPPDATA%\meshbay\  (node.toml, keystore.enc, unlock.key, data/) --
+;     the keystore must survive an uninstall/reinstall; installers place files,
+;     never remove secrets.
+
+!macro customInstall
+  ; resources\node-runtime\meshbay-node.exe is overwritten by this install; a
+  ; daemon still running from a previous version holds the file open.
+  nsExec::Exec 'taskkill /IM meshbay-node.exe /F'
+!macroend
+
+!macro customUnInstall
+  nsExec::Exec 'taskkill /IM meshbay-node.exe /F'
+  ; meshbay_node.platform._startup_vbs() -- if the user ran "meshbay-node
+  ; autostart install" (or toggled it in the client), this points wscript at
+  ; the binary we are about to delete, and would error at every sign-in.
+  Delete "$APPDATA\Microsoft\Windows\Start Menu\Programs\Startup\MeshBay Node.vbs"
+!macroend
diff --git a/packages/meshbay-client/package.json b/packages/meshbay-client/package.json
index 42af9c5..57acff8 100644
--- a/packages/meshbay-client/package.json
+++ b/packages/meshbay-client/package.json
@@ -10,7 +10,8 @@
   "scripts": {
     "start": "electron .",
     "sync-ui": "node scripts/sync-ui.js",
-    "dist": "bash ../../packaging/build/build-client.sh"
+    "dist": "bash ../../packaging/build/build-client.sh",
+    "dist:win": "powershell -NoProfile -ExecutionPolicy Bypass -File ../../packaging/win/build-win.ps1"
   },
   "devDependencies": {
     "electron": "^44.1.1",
@@ -22,7 +23,29 @@
     "files": [
       "src/**",
       "ui/**"
-    ]
+    ],
+    "win": {
+      "target": "nsis",
+      "icon": "build/icon.ico",
+      "artifactName": "${productName}-Setup-${version}.${ext}",
+      "extraResources": [
+        {
+          "from": "node-runtime",
+          "to": "node-runtime",
+          "filter": ["**/*"]
+        }
+      ]
+    },
+    "nsis": {
+      "oneClick": false,
+      "perMachine": false,
+      "allowElevation": false,
+      "allowToChangeInstallationDirectory": true,
+      "createDesktopShortcut": true,
+      "createStartMenuShortcut": true,
+      "deleteAppDataOnUninstall": false,
+      "runAfterFinish": true
+    }
   },
   "dependencies": {
     "bonjour-service": "^1.4.4",
diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index d341619..bd82342 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -792,7 +792,15 @@ function registerBridge() {
   });
 
   function findNodeBinary() {
-    if (process.platform !== 'win32') {
+    if (process.platform === 'win32') {
+      // A packaged Windows build carries the frozen daemon as an
+      // extraResource (package.json build.win, packaging/win/). Prefer it —
+      // it is the version that shipped with this client.
+      if (app.isPackaged) {
+        const bundled = path.join(process.resourcesPath, 'node-runtime', 'meshbay-node.exe');
+        if (fs.existsSync(bundled)) return bundled;
+      }
+    } else {
       const local = path.join(os.homedir(), '.local', 'bin', 'meshbay-node');
       if (fs.existsSync(local)) return local;
     }