feat(i18n): add Chinese (zh-CN) localization for agent names (#338)

Adds Chinese (zh-CN) localization tooling: agent-names-zh.json translation map (130+ entries) and localize-agents-zh.ps1 PowerShell script for localizing agent names in Copilot agent picker.

scripts/i18n/localize-agents-zh.ps1

@@ -0,0 +1,38 @@
+param(
+    [string[]]$TargetDirs = @(
+        "$env:USERPROFILE\.github\agents",
+        "$env:USERPROFILE\.copilot\agents"
+    )
+)
+
+$mapFile = Join-Path $PSScriptRoot "agent-names-zh.json"
+$map = Get-Content $mapFile -Raw -Encoding UTF8 | ConvertFrom-Json
+
+$totalUpdated = 0
+foreach ($dir in $TargetDirs) {
+    if (-not (Test-Path $dir)) { Write-Warning "Skip (not found): $dir"; continue }
+    $files = Get-ChildItem "$dir\*.md" -ErrorAction SilentlyContinue
+    $updated = 0
+    foreach ($f in $files) {
+        $raw = [System.IO.File]::ReadAllText($f.FullName, [System.Text.Encoding]::UTF8)
+        if (-not $raw.StartsWith("---")) { continue }
+        $endIdx = $raw.IndexOf("---", 3)
+        if ($endIdx -lt 0) { continue }
+        $yaml = $raw.Substring(3, $endIdx - 3)
+        if (-not ($yaml -match "(?m)^name:\s*(.+)$")) { continue }
+        $currentName = $Matches[1].Trim()
+        $entry = $map.$currentName
+        if (-not $entry) { continue }
+        $newYaml = $yaml -replace "(?m)^name:\s*.+$", "name: $($entry.name)"
+        if ($newYaml -match "(?m)^description:") {
+            $newYaml = $newYaml -replace "(?m)^description:\s*.+$", "description: $($entry.description)"
+        }
+        $newContent = "---" + $newYaml + "---" + $raw.Substring($endIdx + 3)
+        [System.IO.File]::WriteAllText($f.FullName, $newContent, [System.Text.Encoding]::UTF8)
+        $updated++
+    }
+    Write-Host "OK: $updated agents localized -> $dir"
+    $totalUpdated += $updated
+}
+Write-Host "Total: $totalUpdated agent files updated."
+Write-Host "Reload VS Code window (Ctrl+Shift+P -> Reload Window) to apply."