fix(install): don't abort install.ps1 when git writes to stderr (#80834)

PowerShell 7+ honors $ErrorActionPreference=Stop for native commands,
so git's normal progress line ("From https://...") on stderr during
`git pull --rebase` would turn into a terminating error and abort the
installer immediately after a fresh clone — before pnpm install/build
ever runs. The existing `2>$null` redirects the display but the error
record is still generated.

Wrap the git status / pull calls in try/catch so the pull stays
best-effort and the rest of the installer can proceed. Reproduced on
Windows 11 ARM under PowerShell 7.x with -InstallMethod git.

scripts/install.ps1

@@ -568,8 +568,13 @@ function Install-OpenClawFromGit {
     }
 
     if (-not $SkipUpdate) {
-        if (-not (git -C $RepoDir status --porcelain 2>$null)) {
-            git -C $RepoDir pull --rebase 2>$null
+        # PowerShell 7+ surfaces native-command stderr as terminating errors when
+        # $ErrorActionPreference=Stop, so git's normal "From <url>" progress line
+        # would abort the script. Swallow failures here — pull is best-effort.
+        $dirty = $null
+        try { $dirty = git -C $RepoDir status --porcelain 2>$null } catch {}
+        if (-not $dirty) {
+            try { git -C $RepoDir pull --rebase 2>$null } catch {}
         } else {
             Write-Host "[!] Repo is dirty; skipping git pull" -ForegroundColor Yellow
         }