Don't depend on Node anymore (#346)

## Summary
- package `packages/server` as a standalone desktop executable so
Electron and Tauri no longer depend on a system-installed Node runtime
in production
- align Electron and Tauri startup logic around launching the packaged
server, resolving binaries from the user shell, and bundling the same
server resources into both desktop apps
- replace the workspace instance proxy path that used
`@fastify/reply-from` with a direct streaming proxy so packaged
standalone builds can talk to spawned `opencode` instances correctly

## Why
Desktop production builds were still depending on a user-provided Node
runtime to launch `packages/server`, which made packaging less
self-contained and created different behavior across machines. While
moving to a standalone server executable, we also found that
Bun-compiled standalone builds could start `opencode` successfully but
failed when proxying requests to those instances through `reply-from`.

The goal of this change is to make desktop production startup
self-contained, keep Electron and Tauri behavior aligned, and restore
correct communication with local `opencode` instances in packaged
builds.

## What Changed
- added a standalone build path for `packages/server` and bundle
`codenomad-server` into desktop resources
- updated Electron production startup to resolve and launch the
standalone server executable
- updated Tauri production startup to resolve and launch the standalone
server executable with matching cwd and shell behavior
- added runtime path helpers so the packaged server can reliably find
its bundled UI, auth templates, config template, and package metadata
- improved bare binary resolution so commands like `opencode` can be
resolved from the user's login shell environment
- upgraded the server stack to newer Fastify-compatible packages needed
for the standalone/runtime work
- replaced the workspace instance proxy implementation with a direct
streaming proxy for requests to spawned `opencode` instances
- updated Electron and Tauri build/prebuild scripts to generate and
package the standalone server, while also repairing missing
platform-specific optional binaries during packaging

## Benefits
- desktop production builds no longer require Node to be installed on
the user's system
- Electron and Tauri now use the same packaged server model in
production, reducing platform drift
- packaged desktop apps can successfully create workspaces, launch
`opencode`, and proxy health/session traffic to those instances
- the server bundle is more self-contained and resilient to different
launch environments
- desktop packaging is more predictable because the required server
executable is built and bundled as part of the app build flow

packages/server/package.json

@@ -18,6 +18,7 @@
   },
   "scripts": {
     "build": "npm run build:ui && npm run prepare-ui && tsc -p tsconfig.json && node ./scripts/copy-auth-pages.mjs && npm run prepare-config",
+    "build:standalone": "node ./scripts/build-standalone.mjs",
     "build:ui": "npm run build --prefix ../ui",
     "prepare-ui": "node ./scripts/copy-ui-dist.mjs",
     "prepare-config": "node ./scripts/copy-opencode-config.mjs",
@@ -25,16 +26,16 @@
     "typecheck": "tsc --noEmit -p tsconfig.json"
   },
   "dependencies": {
-    "@fastify/cors": "^8.5.0",
-    "@fastify/reply-from": "^9.8.0",
-    "@fastify/static": "^7.0.4",
+    "@fastify/cors": "^11.2.0",
+    "@fastify/reply-from": "^12.6.2",
+    "@fastify/static": "^9.1.1",
     "commander": "^12.1.0",
-    "fastify": "^4.28.1",
+    "fastify": "^5.8.5",
     "fuzzysort": "^2.0.4",
     "node-forge": "^1.3.3",
     "openai": "^6.27.0",
     "pino": "^9.4.0",
-    "undici": "^6.19.8",
+    "undici": "^8.1.0",
     "yaml": "^2.4.2",
     "yauzl": "^2.10.0",
     "zod": "^3.23.8"
@@ -42,6 +43,7 @@
   "devDependencies": {
     "@types/node-forge": "^1.3.14",
     "@types/yauzl": "^2.10.0",
+    "bun": "^1.3.13",
     "cross-env": "^7.0.3",
     "ts-node": "^10.9.2",
     "tsx": "^4.20.6",