fix: add windowsHide:true to remaining spawn/exec calls to prevent CMD flash on Windows

Previous fixes in #6813 and subsequent PRs added windowsHide:true to most
spawn sites, but several call sites were missed or regressed:

- SDK server.ts (v1 + v2): kilo serve and TUI spawn
- ts-check.ts: Bun.spawn for tsc invocation
- github.ts: exec for browser open
- desktop-electron cli.ts: install script spawn and version check
- desktop-electron ipc.ts: open-path execFile
- desktop-electron apps.ts: wsl/where execFileSync calls

Without windowsHide:true, each of these subprocess invocations causes a
visible cmd.exe console window to briefly flash on Windows.

Closes #7896

packages/opencode/src/cli/cmd/github.ts

@@ -330,7 +330,7 @@ export const GithubInstallCommand = cmd({
                   ? `start "" "${url}"`
                   : `xdg-open "${url}"`
 
-            exec(command, (error) => {
+            exec(command, { windowsHide: true }, (error) => {
               if (error) {
                 prompts.log.warn(`Could not open browser. Please visit: ${url}`)
               }